Chemistry 9th Chap 3 : Topic 1 - Maryam Publications

Chemistry Chapter 3 : Topic 1

Structure of Atom

1 / 20

Which statement best explains why almost all the mass of an atom is concentrated in a very small central region?

A) Because protons and neutrons, which have significant mass, are located in the nucleus

B) Because shells are densely packed with electrons

C) Because electrons move very fast in shells, increasing their effective mass

D) Because empty space between electrons contributes to atomic mass

2 / 20

If the nucleus of an atom were removed, which property of the atom would be most directly affected?

A) Electron arrangement in shells

B) Electrical neutrality

C) Chemical reactivity

D) Atomic mass

3 / 20

In an atom, electrons revolve around the nucleus in specific energy levels. These levels are called shells because:

A) They are hard spherical coverings around the nucleus

B) They represent fixed paths with defined energy for electrons

C) They prevent electrons from interacting with each other

D) They are regions filled with protons and neutrons

4 / 20

Which observation from atomic structure supports the idea that atoms are mostly empty space?

A) Electrons have negligible mass

B) Electrons are negatively charged

C) The nucleus occupies a very small volume compared to the whole atom

D) Protons and neutrons are closely packed

5 / 20

Which statement correctly relates the number of protons and electrons in a neutral atom?

A) Number of protons equals number of electrons

B) Number of protons is always greater than electrons

C) Number of electrons is independent of protons

D) Number of neutrons equals number of electrons

6 / 20

Why do electrons not collapse into the nucleus despite the electrostatic attraction between opposite charges?

A) Because electrons move in defined energy levels that maintain stability

B) Because electrons have no mass

C) Because protons neutralize electron charge

D) Because neutrons repel electrons

7 / 20

Which comparison correctly describes protons and neutrons in the nucleus?

A) Both have equal mass but neutrons have no charge

B) Both have equal mass and equal charge

C) Neutrons are lighter and negatively charged

D) Protons are heavier than neutrons and carry positive charge

8 / 20

An atom has 2 electrons in the first shell and 8 in the second shell. Which conclusion is most appropriate?

A) The atom follows the shell structure with limited electron capacity

B) The atom has no nucleus

C) The atom is unstable because shells are incomplete

D) The atom must have equal neutrons and protons

9 / 20

Which statement best explains the role of neutrons in the nucleus?

A) They determine chemical properties

B) They balance positive charge of protons

C) They move in shells like electrons

D) They contribute to mass and stability of nucleus

10 / 20

If an atom loses one electron, what happens to its overall charge?

A) It remains neutral

B) It becomes positively charged

C) It loses mass significantly

D) It becomes negatively charged

11 / 20

Which part of the atom determines its identity (element type)?

A) Number of neutrons

B) Number of protons in nucleus

C) Number of shells

D) Number of electrons in outer shell

12 / 20

Why are electrons arranged in different shells rather than randomly around the nucleus?

A) Because protons push electrons outward

B) Because shells have different colors

C) Because electrons occupy specific energy levels

D) Because neutrons attract electrons

13 / 20

Which statement best distinguishes electrons from protons and neutrons?

A) Electrons are neutral particles

B) Electrons are located in the nucleus

C) Electrons have significant mass

D) Electrons move in shells outside the nucleus

14 / 20

If the number of neutrons in an atom changes but protons remain the same, what is affected?

A) Atomic mass

B) Chemical identity

C) Atomic charge

D) Electron configuration

15 / 20

Which conclusion can be drawn about the nucleus due to the presence of positively charged protons?

A) It repels electrons

B) It attracts electrons

C) It neutralizes electron charge completely

D) It has no effect on electrons

16 / 20

Which of the following best explains why electrons are considered to have negligible mass?

A) They are neutral particles

B) They are located far from nucleus

C) They do not exist in atoms

D) Their mass is extremely small compared to protons and neutrons

17 / 20

Which structural feature ensures that electrons remain at specific distances from the nucleus?

A) Neutron distribution

B) Atomic mass

C) Electron shells (energy levels)

D) Proton repulsion

18 / 20

Which statement best explains the term “central nucleus”?

A) It is the dense core containing protons and neutrons

B) It is the outermost region of atom

C) It is made of empty space

D) It contains only electrons

19 / 20

Why do protons remain together in the nucleus despite repulsive forces between them?

A) Because protons have no charge

B) Because electrons neutralize them

C) Because neutrons help stabilize and hold nucleus together

D) Because shells push them inward

20 / 20

Which statement best describes the arrangement of particles in an atom?

A) Protons orbit electrons

B) Neutrons move in shells

C) Electrons surround a central nucleus containing protons and neutrons

D) All particles are randomly distributed

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