Question 1

Which experiment led to the discovery of the atomic nucleus, and what was the key observation that supported this discovery?

Accepted Answer

The gold foil experiment; the observation that a small fraction of alpha particles were deflected at large angles.

Question 2

According to Dalton’s atomic theory, which statement is INCORRECT based on modern understanding?

Accepted Answer

Atoms of the same element are identical in mass and properties.

Question 3

Which of the following best explains why atoms are important in chemistry?

Accepted Answer

Atoms are the smallest units of matter that retain the properties of an element.

Question 4

Which subatomic particle was discovered using cathode ray tubes, and what property did this experiment reveal?

Accepted Answer

Electron; its negative charge

Question 5

What is the significance of the emission spectrum of hydrogen in understanding atomic structure?

Accepted Answer

It shows that electrons occupy discrete energy levels.

Question 6

Which of the following statements about the periodic table is correct?

Accepted Answer

Each element is defined by its number of protons, also known as the atomic number.

Question 7

If an atom has 11 protons, 12 neutrons, and 11 electrons, what is its atomic number and mass number?

Accepted Answer

Atomic number = 11, Mass number = 23

Question 8

Which equation correctly represents the relationship between the speed of light $$(c)$$, wavelength $$(\lambda)$$, and frequency $$(
u) of $$light?

Accepted Answer

$$c = \lambda 
u$$

Question 9

Why did Rutherford conclude that the atom is mostly empty space?

Accepted Answer

Most alpha particles passed straight through the gold foil with little or no deflection.

Question 10

Which of the following best describes the charge and location of protons, neutrons, and electrons in an atom?

Accepted Answer

Protons and neutrons are in the nucleus; electrons are outside the nucleus.

Question 11

Which property of electrons allows them to be deflected by electric and magnetic fields?

Accepted Answer

Their negative charge

Question 12

A neutral atom of carbon has 6 protons. How many electrons does it have?

Accepted Answer

6

Question 13

Which of the following is a real-world application of understanding atomic structure?

Accepted Answer

Developing new materials for electronics and medicine

Question 14

Which scientist is credited with the first modern atomic theory based on experimental evidence?

Accepted Answer

John Dalton

Question 15

What is the relative mass and charge of a neutron?

Accepted Answer

Relative mass = 1, Charge = 0

Question 16

Which of the following best describes the difference between an atom and an element?

Accepted Answer

An element is a substance made of only one kind of atom.

Question 17

Which of the following is NOT a postulate of Dalton’s atomic theory?

Accepted Answer

Atoms can be divided into protons, neutrons, and electrons.

Question 18

If an atom has 17 protons, 18 neutrons, and 17 electrons, what is its atomic number and what element is it?

Accepted Answer

Atomic number = 17, Element = Chlorine

Question 19

Which of the following best explains why the periodic table is useful for chemists?

Accepted Answer

It organizes elements by their atomic number and similar chemical properties.

Question 20

Which of the following statements about the nucleus of an atom is correct?

Accepted Answer

It contains most of the atom’s mass.

Class 2, Ch. 5.1: Atoms and Elements

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