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Structure of atoms
10 Class 9 Chemistry questions with answers and explanations.
Printable worksheet with answer key
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Which particle in an atom has a negative charge?
- 1 Nucleus
- 2 Neutron
- 3 Electron
- 4 Proton
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The atomic number of an element is the number of:
- 1 Neutrons
- 2 Protons
- 3 Shells
- 4 Protons plus neutrons
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Correct answer: Protons
The atomic number equals the number of protons.
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An atom has 11 protons and 12 neutrons. What is its mass number?
- 1 12
- 2 1
- 3 23
- 4 11
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Atoms of the same element with different numbers of neutrons are called:
- 1 Isomers
- 2 Isotopes
- 3 Isobars
- 4 Ions
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Correct answer: Isotopes
These are isotopes: same atomic number, different mass number.
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What is the electronic configuration of sodium (atomic number 11)?
- 1 8, 3
- 2 2, 9
- 3 2, 8, 2
- 4 2, 8, 1
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Correct answer: 2, 8, 1
Fill shells 2, 8, then the remaining 1 electron goes in the third shell.
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Which scientist discovered the nucleus?
- 1 Bohr
- 2 Dalton
- 3 Rutherford
- 4 Thomson
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Correct answer: Rutherford
Rutherford's gold foil experiment showed that atoms have a small dense nucleus.
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The number of electrons in a neutral atom equals its number of:
- 1 Protons
- 2 Nucleons
- 3 Shells
- 4 Neutrons
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Correct answer: Protons
A neutral atom has equal protons and electrons.
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The maximum number of electrons in the first shell is:
- 1 8
- 2 18
- 3 2
- 4 1
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Which particle has no charge?
- 1 Positron
- 2 Electron
- 3 Neutron
- 4 Proton
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Chlorine has isotopes with mass numbers 35 and 37. They differ in the number of:
- 1 Electrons
- 2 Shells
- 3 Protons
- 4 Neutrons