brodidit for students
Structure of atoms
Class 9 · Chemistry · 6 questions
Name: ____________________ Date: ____________
Which particle in an atom has a negative charge?
- A Nucleus
- B Neutron
- C Electron
- D Proton
The atomic number of an element is the number of:
- A Neutrons
- B Protons
- C Shells
- D Protons plus neutrons
An atom has 11 protons and 12 neutrons. What is its mass number?
- A 12
- B 1
- C 23
- D 11
Atoms of the same element with different numbers of neutrons are called:
- A Isomers
- B Isotopes
- C Isobars
- D Ions
What is the electronic configuration of sodium (atomic number 11)?
- A 8, 3
- B 2, 9
- C 2, 8, 2
- D 2, 8, 1
Which scientist discovered the nucleus?
- A Bohr
- B Dalton
- C Rutherford
- D Thomson
Answer key
1. C, 2. B, 3. C, 4. B, 5. D, 6. C
Electrons carry a negative charge.
The atomic number equals the number of protons.
Mass number = protons + neutrons = 11 + 12 = 23.
These are isotopes: same atomic number, different mass number.
Fill shells 2, 8, then the remaining 1 electron goes in the third shell.
Rutherford's gold foil experiment showed that atoms have a small dense nucleus.