Atoms and Elements

Question 1

What is the nucleus made up of?

Answer 1

The nucleus is made up of protons and neutrons.

Question 2

How to calculate the mass number of an atom?

Answer 2

Mass no. = Protons + Neutrons.
(We don’t count electrons as their mass is so small that their contribution to mass no. is considered insignificant)

Question 3

What is the KLMN rule for electron configuration?

Answer 3

The KLMN rule:
- First shell: 2 electrons
- Second shell: 8 electrons
- Third shell: 8 electrons
- Fourth shell: 2 electrons
- After 20 electrons total, 10 more electrons fill the Third shell (making its total 18 electrons)
- After that, the Fourth electron shell should fill up to 32 electrons.

Question 4

What is the formula for mass no.?

Answer 4

Mass number = Protons + Neutrons

Question 5

What is the formula to find the number of neutrons in an atom?

Answer 5

No. of neutrons = Mass number - Atomic number

Question 6

TRUE or FALSE: The Atomic number will ALWAYS be smaller than the mass number.

Answer 6

TRUE

Question 7

Where is the mass number located, if the atomic number is a small value at the bottom, and the element symbol is a big, main value at the middle?

Answer 7

The mass number is a small number on top left of the element symbol.

Question 8

What are isotopes?

Answer 8

Isotopes are the same elements with different mass numbers. (eg. Carbon-12 having 6 neutrons and Carbon-14 having 8 electrons).