Problem-Solving and Data Analysis - Set - 1
SAT - Math Section - Problem-Solving and Data Analysis - Set - 1
Geometry and Trigonometry - Set - 1
SAT - Math Section - Geometry and Trigonometry - Set - 1
Information and Ideas - Set - 1
SAT - The Reading and Writing Section - Information and Ideas - Set - 1
Expression of Ideas - Set - 1
Premium ContentSAT - The Reading and Writing Section - Expression of Ideas - Set - 1
Craft and Structure - Set - 1
SAT - The Reading and Writing Section - Craft and Structure - Set - 1
Standard English Conventions - Set - 1
SAT - The Reading and Writing Section - Standard English Conventions - Set - 1
Review 1 - Unit 1-4 - Notes
Class 09 - English - Review 1 - Unit 1-4 - Notes
Unit 1 - The Saviour of Mankind - Notes
Class 09 - English - Unit 1 - The Saviour of Mankind - Notes
Nazm 1 - Hamd - Majmooyi Jaiza
Class 09 - Urdu - Nazm 1 - Hamd - Majmooyi Jaiza
Ghazal 1 - Hasti Apni Habab Ki Si Hai - Tashrih
Class 09 - Urdu - Ghazal 1 - Hasti Apni Habab Ki Si Hai - Tashrih
Ghazal 1 - Hasti Apni Habab Ki Si Hai - Mashq
Class 09 - Urdu - Ghazal 1 - Hasti Apni Habab Ki Si Hai - Mashq
Ghazal 1 - Hasti Apni Habab Ki Si Hai - Majmooyi Jaiza
Class 09 - Urdu - Ghazal 1 - Hasti Apni Habab Ki Si Hai - Majmooyi Jaiza
Chapter 12 - Hausla Na Haaro Agay Barho - Mashq
Class 09 - Urdu - Chapter 12 - Hausla Na Haaro Agay Barho - Mashq
Chapter 11 - Qadr e Ayaz - Tashrih
Class 09 - Urdu - Chapter 11 - Qadr e Ayaz - Tashrih
Chapter 11 - Qadr e Ayaz - Mashq
Class 09 - Urdu - Chapter 11 - Qadr e Ayaz - Mashq
Chapter 11 - Qadr e Ayaz - Majmooyi Jaiza
Class 09 - Urdu - Chapter 11 - Qadr e Ayaz - Majmooyi Jaiza
Chapter 10 - Mulki Parinday aur Doosray Janwar - Tashrih
Class 09 - Urdu - Chapter 10 - Mulki Parinday aur Doosray Janwar - Tashrih
Class 09 FBISEUrduChapter 10 - Mulki Parinday aur Doosray Janwar
Chapter 10 - Mulki Parinday aur Doosray Janwar - Mashq
Class 09 - Urdu - Chapter 10 - Mulki Parinday aur Doosray Janwar - Mashq
Class 09 FBISEUrduChapter 10 - Mulki Parinday aur Doosray Janwar
Chapter 10 - Mulki Parinday aur Doosray Janwar - Majmooyi Jaiza
Class 09 - Urdu - Chapter 10 - Mulki Parinday aur Doosray Janwar - Majmooyi Jaiza
Class 09 FBISEUrduChapter 10 - Mulki Parinday aur Doosray Janwar
Chapter 9 - Imtehaan - Tashrih
Class 09 - Urdu - Chapter 9 - Imtehaan - Tashrih
Chapter 9 - Imtehaan - Mashq
Class 09 - Urdu - Chapter 9 - Imtehaan - Mashq
Chapter 9 - Imtehaan - Majmooyi Jaiza
Class 09 - Urdu - Chapter 9 - Imtehaan - Majmooyi Jaiza
Chapter 8 - Lahu aur Qaleen - Tashrih
Class 09 - Urdu - Chapter 8 - Lahu aur Qaleen - Tashrih
Chapter 8 - Lahu aur Qaleen - Mashq
Class 09 - Urdu - Chapter 8 - Lahu aur Qaleen - Mashq
Chapter 8 - Lahu aur Qaleen - Majmooyi Jaiza
Class 09 - Urdu - Chapter 8 - Lahu aur Qaleen - Majmooyi Jaiza
Chapter 7 - Araam o Sukoon - Tashrih
Class 09 - Urdu - Chapter 7 - Araam o Sukoon - Tashrih
Chapter 7 - Araam o Sukoon - Mashq
Class 09 - Urdu - Chapter 7 - Araam o Sukoon - Mashq
Chapter 7 - Araam o Sukoon - Majmooyi Jaiza
Class 09 - Urdu - Chapter 7 - Araam o Sukoon - Majmooyi Jaiza
Chapter 6 - Panchaiyat - Tashrih
Class 09 - Urdu - Chapter 6 - Panchaiyat - Tashrih
Chapter 6 - Panchaiyat - Mashq
Class 09 - Urdu - Chapter 6 - Panchaiyat - Mashq
Chapter 6 - Panchaiyat - Majmooyi Jaiza
Class 09 - Urdu - Chapter 6 - Panchaiyat - Majmooyi Jaiza
Chapter 5 - Nasoo aur Saleem ki Guftugu - Tashrih
Class 09 - Urdu - Chapter 5 - Nasoo aur Saleem ki Guftugu - Tashrih
Chapter 5 - Nasoo aur Saleem ki Guftugu - Mashq
Class 09 - Urdu - Chapter 5 - Nasoo aur Saleem ki Guftugu - Mashq
Chapter 5 - Nasoo aur Saleem ki Guftugu - Majmooyi Jaiza
Class 09 - Urdu - Chapter 5 - Nasoo aur Saleem ki Guftugu - Majmooyi Jaiza
Chapter 4 - Shairoo k Lateefay - Tashrih
Class 09 - Urdu - Chapter 4 - Shairoo k Lateefay - Tashrih
Chapter 4 - Shairoo k Lateefay - Mashq
Class 09 - Urdu - Chapter 4 - Shairoo k Lateefay - Mashq
Chapter 4 - Shairoo k Lateefay - Majmooyi Jaiza
Class 09 - Urdu - Chapter 4 - Shairoo k Lateefay - Majmooyi Jaiza
Chapter 3 - Kahili - Tashrih
Class 09 - Urdu - Chapter 3 - Kahili - Tashrih
Chapter 3 - Kahili - Mashq
Class 09 - Urdu - Chapter 3 - Kahili - Mashq
Chapter 3 - Kahili - Majmooyi Jaiza
Class 09 - Urdu - Chapter 3 - Kahili - Majmooyi Jaiza
Chapter 2 - Mirza Ghalib k Aadaat o Khasail - Tashrih
Class 09 - Urdu - Chapter 2 - Mirza Ghalib k Aadaat o Khasail - Tashrih
Class 09 FBISEUrduChapter 2 - Mirza Ghalib k Aadaat o Khasail
Chapter 2 - Mirza Ghalib k Aadaat o Khasail - Mashq
Class 09 - Urdu - Chapter 2 - Mirza Ghalib k Aadaat o Khasail - Mashq
Class 09 FBISEUrduChapter 2 - Mirza Ghalib k Aadaat o Khasail
Chapter 2 - Mirza Ghalib k Aadaat o Khasail - Majmooyi Jaiza
Class 09 - Urdu - Chapter 2 - Mirza Ghalib k Aadaat o Khasail - Majmooyi Jaiza
Class 09 FBISEUrduChapter 2 - Mirza Ghalib k Aadaat o Khasail
Chapter 1 - Hijrat e Nabwi - Tashrih
Class 09 - Urdu - Chapter 1 - Hijrat e Nabwi - Tashrih
Chapter 1 - Hijrat e Nabwi - Mashq
Class 09 - Urdu - Chapter 1 - Hijrat e Nabwi - Mashq
Chapter 1 - Hijrat e Nabwi - Majmooyi Jaiza
Class 09 - Urdu - Chapter 1 - Hijrat e Nabwi - Majmooyi Jaiza
Grammar - Grammar Important Questions - Set 1
Premium ContentClass 09 - Urdu - Grammar - Grammar Important Questions - Set 1
Ghazal 1 - Musibat Bhi Rahat Fiza Hogyi Hai - Mashq
Class 10 - Urdu - Ghazal 1 - Musibat Bhi Rahat Fiza Hogyi Hai - Mashq
Class 10 FBISEUrduGhazal 1 - Musibat Bhi Rahat Fiza Hogyi Hai
Ghazal 1 - Musibat Bhi Rahat Fiza Hogyi Hai - Tashrih
Class 10 - Urdu - Ghazal 1 - Musibat Bhi Rahat Fiza Hogyi Hai - Tashrih
Class 10 FBISEUrduGhazal 1 - Musibat Bhi Rahat Fiza Hogyi Hai
Ghazal 1 - Musibat Bhi Rahat Fiza Hogyi Hai - Majmooyi Jaiza
Class 10 - Urdu - Ghazal 1 - Musibat Bhi Rahat Fiza Hogyi Hai - Majmooyi Jaiza
Class 10 FBISEUrduGhazal 1 - Musibat Bhi Rahat Fiza Hogyi Hai
Nazam 2 - Maidan e Karbala Mein Grmi Ki Shidat - Mashq
Class 10 - Urdu - Nazam 2 - Maidan e Karbala Mein Grmi Ki Shidat - Mashq
Class 10 FBISEUrduNazam 2 - Maidan e Karbala Mein Grmi Ki Shidat
Nazam 2 - Maidan e Karbala Mein Grmi Ki Shidat - Tashrih
Class 10 - Urdu - Nazam 2 - Maidan e Karbala Mein Grmi Ki Shidat - Tashrih
Class 10 FBISEUrduNazam 2 - Maidan e Karbala Mein Grmi Ki Shidat
Nazam 2 - Maidan e Karbala Mein Grmi Ki Shidat - Majmooyi Jaiza
Class 10 - Urdu - Nazam 2 - Maidan e Karbala Mein Grmi Ki Shidat - Majmooyi Jaiza
Class 10 FBISEUrduNazam 2 - Maidan e Karbala Mein Grmi Ki Shidat
Nazam 1 - Bahadur Bachay - Majmooyi Jaiza
Class 10 - Urdu - Nazam 1 - Bahadur Bachay - Majmooyi Jaiza
Unit 14 - Khatoot-e-Rasheed Ahmed Siddiqui - Mashq
Class 10 - Urdu - Unit 14 - Khatoot-e-Rasheed Ahmed Siddiqui - Mashq
Class 10 FBISEUrduUnit 14 - Khatoot-e-Rasheed Ahmed Siddiqui
Unit 14 - Khatoot-e-Rasheed Ahmed Siddiqui - Majmooyi Jaiza
Class 10 - Urdu - Unit 14 - Khatoot-e-Rasheed Ahmed Siddiqui - Majmooyi Jaiza
Class 10 FBISEUrduUnit 14 - Khatoot-e-Rasheed Ahmed Siddiqui
Unit 13 - Khatoot-e-Ghalib - Mashq
Class 10 - Urdu - Unit 13 - Khatoot-e-Ghalib - Mashq
Unit 13 - Khatoot-e-Ghalib - Majmooyi Jaiza
Class 10 - Urdu - Unit 13 - Khatoot-e-Ghalib - Majmooyi Jaiza
Unit 1 - Hamd - Majmooyi Jaiza
Class 10 - Urdu - Unit 1 - Hamd - Majmooyi Jaiza
Important MCQs - Set - 1
Class 11 - Urdu - Important MCQs - Set - 1
Class 11 FBISEUrduImportant MCQsImportant Questions from Past FBISE Papers
Important Objective Questions - Set - 1
Class 11 - Urdu - Important Objective Questions - Set - 1
Class 11 FBISEUrduImportant Objective QuestionsImportant Questions from Past FBISE Papers
Ghazal 1 - Peeri Mein Kia Jawani K Mausam Ko Royie - Tashrih
Class 11 - Urdu - Ghazal 1 - Peeri Mein Kia Jawani K Mausam Ko Royie - Tashrih
Ghazal 1 - Peeri Mein Kia Jawani K Mausam Ko Royie - Mashq
Class 11 - Urdu - Ghazal 1 - Peeri Mein Kia Jawani K Mausam Ko Royie - Mashq
Ghazal 1 - Faqirana Aye Sada Kar Chalay - Tashrih
Class 11 - Urdu - Ghazal 1 - Faqirana Aye Sada Kar Chalay - Tashrih
Ghazal 1 - Faqirana Aye Sada Kar Chalay - Mashq
Class 11 - Urdu - Ghazal 1 - Faqirana Aye Sada Kar Chalay - Mashq
Nazm 8 - Naseehat e Ikhlaaqi - Tashrih
Class 11 - Urdu - Nazm 8 - Naseehat e Ikhlaaqi - Tashrih
Nazm 8 - Naseehat e Ikhlaaqi - Mashq
Class 11 - Urdu - Nazm 8 - Naseehat e Ikhlaaqi - Mashq
Nazm 6 - Takht e Faras Pe Ali Akbar Ka Khitaab - Tashrih
Class 11 - Urdu - Nazm 6 - Takht e Faras Pe Ali Akbar Ka Khitaab - Tashrih
Nazm 6 - Takht e Faras Pe Ali Akbar Ka Khitaab - Mashq
Class 11 - Urdu - Nazm 6 - Takht e Faras Pe Ali Akbar Ka Khitaab - Mashq
Nazm 5 - Dur e Murad - Tashrih
Class 11 - Urdu - Nazm 5 - Dur e Murad - Tashrih
Nazm 5 - Dur e Murad - Mashq
Class 11 - Urdu - Nazm 5 - Dur e Murad - Mashq
Chapter 15 - Allama Iqbal - Mashq
Class 11 - Urdu - Chapter 15 - Allama Iqbal - Mashq
Chapter 14 - Makateeb - Mirza Ghalib - Mashq
Class 11 - Urdu - Chapter 14 - Makateeb - Mirza Ghalib - Mashq
Chapter 13 - Lalchi Wazeer - Mashq
Class 11 - Urdu - Chapter 13 - Lalchi Wazeer - Mashq
Chapter 12 - Rome - Zinda Shehar, Murda Shehar - Mashq
Class 11 - Urdu - Chapter 12 - Rome - Zinda Shehar, Murda Shehar - Mashq
Chapter 11 - Shairaz Aur Kanar Aab Rukna Badu Waghaira - Mashq
Class 11 - Urdu - Chapter 11 - Shairaz Aur Kanar Aab Rukna Badu Waghaira - Mashq
Chapter 10 - Taleem e Balighan - Mashq
Class 11 - Urdu - Chapter 10 - Taleem e Balighan - Mashq
Chapter 9 - Khoobsurat Bala - Mashq
Class 11 - Urdu - Chapter 9 - Khoobsurat Bala - Mashq
Chapter 7 - Darogha Ji Ki Panchoo Ghee Mein Aur Sir Karahi Mein - Mashq
Class 11 - Urdu - Chapter 7 - Darogha Ji Ki Panchoo Ghee Mein Aur Sir Karahi Mein - Mashq
Class 11 FBISEUrduDarogha Ji Ki Panchoo Ghee Mein Aur Sir Karahi Mein
Chapter 6 - Lamha e Fikriya - Mashq
Class 11 - Urdu - Chapter 6 - Lamha e Fikriya - Mashq
Chapter 5 - Kuch Adab K Baray Mein - Mashq
Class 11 - Urdu - Chapter 5 - Kuch Adab K Baray Mein - Mashq
Chapter 4 - Pakistani Qomiat Ka Masla - Mashq
Class 11 - Urdu - Chapter 4 - Pakistani Qomiat Ka Masla - Mashq
Chapter 3 - Nazria e Pakistan - Mashq
Class 11 - Urdu - Chapter 3 - Nazria e Pakistan - Mashq
Chapter 2 - Jhootay Aadmi - Mashq
Class 11 - Urdu - Chapter 2 - Jhootay Aadmi - Mashq
Chapter 1 - Apni Madad Aap - Mashq
Class 11 - Urdu - Chapter 1 - Apni Madad Aap - Mashq
Important Questions From Past Papers - Set - 1
Class 12 - Urdu - Important Questions From Past Papers - Set - 1
Class 12 FBISEUrduImportant Objective QuestionsImportant MCQsImportant Questions from Past FBISE Papers
Nazm 6 - Nafeer-e-Amal - Tashrih
Class 12 - Urdu - Nazm 6 - Nafeer-e-Amal - Tashrih
Nazm 6 - Nafeer-e-Amal - Mashq
Class 12 - Urdu - Nazm 6 - Nafeer-e-Amal - Mashq
Nazm 3 - Manazir-e-Sahar - Tashrih
Class 12 - Urdu - Nazm 3 - Manazir-e-Sahar - Tashrih
Nazm 3 - Manazir-e-Sahar - Mashq
Class 12 - Urdu - Nazm 3 - Manazir-e-Sahar - Mashq
Nazm 1 - Jawab-e-Shiqva - Tashrih
Class 12 - Urdu - Nazm 1 - Jawab-e-Shiqva - Tashrih
A method used to prevent rusting in ships and underground pipelines involves connecting the iron to a block of a more active metal such as magnesium. This method is called cathodic protection. How many moles of magnesium are present in 1 billion (1 x 109) atoms of magnesium?
Chemistry - Fundamentals of Chemistry - A method used to prevent rusting in ships and underground pipelines involves connecting the iron to a block of a more active metal such as magnesium. This method is called cathodic protection. How many moles of magnesium are present in 1 billion (1 x 109) atoms of magnesium?
How many atoms are there in 1 mole of Sulphur atoms?
Chemistry - Fundamentals of Chemistry - How many atoms are there in 1 mole of Sulphur atoms?
How many atoms are there in 32.1 g of S-atoms?
Chemistry - Fundamentals of Chemistry - How many atoms are there in 32.1 g of S-atoms?
The simplest ratio between C, H and O atoms in glucose in 1:2:1. What is the empirical formula of glucose?
Chemistry - Fundamentals of Chemistry - The simplest ratio between C, H and O atoms in glucose in 1:2:1. What is the empirical formula of glucose?
Write the notes and comments on the chapter "Three days to see".
Class 09 FBISE English - Three days to see -Write the notes and comments on the chapter Three days to see
If $\left[ \begin{matrix} a+3 & 4 \\ 6 & b-1 \\ \end{matrix} \right]=\left[ \begin{matrix} -3 & 4 \\ 6 & 2 \\ \end{matrix} \right]$ , then find a and b.
Class 09 FBISE Mathematics - Matrices and Determinants - find a and b
What is the theme of the chapter "Drug addiction"?
Class 09 FBISE English - Drug addiction -What is the theme of the chapter Drug addiction
Write an essay on "Quaid-e-Azam-Our National Hero".
Class 09 FBISE English - Quaids vision and Pakistan -Write an essay on Quaid e Azam Our National Hero
Write a paragraph on Quaid-e-Azam as a progressive and moderate democrat.
Class 09 FBISE English - Quaids vision and Pakistan -Write a paragraph on Quaid e Azam as a progressive and moderate democrat
What was the ideology of Pakistan in view of Quaid-e-Azam?
Class 09 FBISE English - Quaids vision and Pakistan -What was the ideology of Pakistan in view of Quaid e Azam
How much confidence did Quaid-e-Azam have in his nation?
Class 09 FBISE English - Quaids vision and Pakistan -How much confidence did Quaid e Azam have in his nation
Why did Quaid-e-Azam ignore his ever-failing health?
Class 09 FBISE English - Quaids vision and Pakistan -Why did Quaid e Azam ignore his ever failing health
Find negative of matrices A, B, C, D and E when
Class 09 FBISE Mathematics - Matrices and Determinants - Find negative of matrices A, B, C, D and E when
From the following matrices, identify (a) Square matrices (b) Rectangular matrices (c) Row matrices (d) Column matrices (e) Identity matrices (f) Null matrices
Class 09 FBISE Mathematics- Matrices and Determinants - identify Square matrices, Rectangular matrices, Row matrices, Column matrices, Identity matrices, Null matrices
What is the theme of the chapter "Hazrat Asma"
Class 09 FBISE English - Hazrat Asma -What is the theme of the chapter Hazrat Asma
Write an e-mail to your friend
Class 09 FBISE English - Media and Its Impact -Write an email to your friend
How will you elaborate Quaid e Azam Muhammad Ali Jinnahs quote
Class 09 FBISE English - Patriotism - How will you elaborate Quaid e Azam Muhammad Ali Jinnahs quote
(i) P.E. at its maximum height (ii) K.E. when it hits the ground
Class 9 FBISE Physics - Work and energy - (i) P.E. at its maximum height (ii) K.E. when it hits the ground
A block of mass 10 kg is suspended at a distance of 20 cm from the center of a uniform bar 1 m long.
Class 9 FBISE Physics - Turning effect of forces - A block of mass 10 kg is suspended at a distance of 20 cm from the center of a uniform bar 1 m long.
How much time is required to change 22 Ns momentum by a force of 20 N? (1.1s)
Class 9 FBISE Physics - Dynamics - How much time is required to change 22 Ns momentum by a force of 20 N? (1.1s)
A car moves with a uniform velocity of 40 $ms^{-1}$ for 5 s. It comes to rest in the next 10 s with uniform deceleration.
Class 9 FBISE Physics - Kinematics - A car moves with a uniform velocity of 40 $ms^{-1}$ for 5 s. It comes to rest in the next 10 s with uniform deceleration.
A tennis ball is hit vertically upward with a velocity of 30 $ms^{-1}$, it takes 3 s to reach the highest point.
Class 9 FBISE Physics - Kinematics - A tennis ball is hit vertically upward with a velocity of 30 $ms^{-1}$, it takes 3 s to reach the highest point.
A train starts from rest. It moves through 1 km in 100 s with uniform acceleration.
Class 9 FBISE Physics - Kinematics - A train starts from rest. It moves through 1 km in 100 s with uniform acceleration.
A train moves with a uniform velocity of 36 $kmh^{-1} for 10s$. Find the distance traveled by it.
Class 9 FBISE Physics - Kinematics - A train moves with a uniform velocity of 36 $kmh^{-1} for 10s$. Find the distance traveled by it.
Your hair grows at the rate of 1 mm per day. Find their growth rate
Class 9 FBISE Physics - Physical Quantities and Measurement - Your hair grows at the rate of 1 mm per day. Find their growth rate
State mass-energy equation $E = mc^{2}$
Class 9 FBISE Physics - Work and energy - State mass-energy equation $E = mc^{2}$
Define K.E. and derive its relation.
Class 9 FBISE Physics - Work and energy - Define K.E. and derive its relation.
Explain the role of Quaid-e-Azam (Rahmatullah) as first Governor-General of Pakistan.
Class 09 FBISE Pakistan Studies - History of Pakistan -Explain the role of Quaid e Azam Rahmatullah as first Governor-General of Pakistan
Describe the role of Quaid-e-Azam (Rahmatullah) in the creation of Pakistan?
Class 09 FBISE Pakistan Studies - Making of Pakistan - Describe the role of Quaid e Azam Rahmatullah in the creation of Pakistan
How did the Quaid e Azam Rahmatullah get the title of Ambassador of Peace
Class 09 FBISE Pakistan Studies - Making of Pakistan - How did the Quaid e Azam Rahmatullah get the title of Ambassador of Peace
Narrate the standpoint of Quaid e Azam
Class 09 FBISE Pakistan Studies - Making of Pakistan - Narrate the standpoint of Quaid e Azam
Elaborate on the Ideology of Pakistan in the light of the Pronouncements of Quaid e Azam Rahmatullah
Class 09 FBISE Pakistan Studies - Making of Pakistan - Elaborate on the Ideology of Pakistan in the light of the Pronouncements of Quaid e Azam Rahmatullah
What did Quaid e Azam Rahmatullah say about the security of minorities
Class 09 FBISE Pakistan Studies - Making of Pakistan - What did Quaid e Azam Rahmatullah say about the security of minorities
While inaugurating the State bank what did Quaid-e-Azam Rahmatullah say
Class 09 FBISE Pakistan Studies - Making of Pakistan - While inaugurating the State bank what did Quaid-e-Azam Rahmatullah say
Show that $Ns = Kg \: m/s$ OR Ns = $Kg \: ms^{-1}$
Class 9 FBISE Physics - Dynamics - Show that $Ns = Kg \: m/s$ OR Ns = $Kg \: ms^{-1}$
Statement 1: All enzymes are catalysts. Statement 2: All catalysts are enzymes. Which one is correct?
Class 9 FBISE Biology - Enzymes - Statement 1: All enzymes are catalysts. Statement 2: All catalysts are enzymes. Which one is correct?
Describe the major plant tissues i.e. simple tissues (meristematic tissues, permanent tissues) and compound tissues (xylem phloem tissues) in terms of their cell specificities, locations, and functions.
Class 9 FBISE Biology - Cells and Tissues - Describe the major plant tissues i.e. simple tissues (meristematic tissues, permanent tissues) and compound tissues (xylem phloem tissues) in terms of their cell specificities, locations, and functions.