Q: Which formula gives the mass number ($$A) of an $$atom?

$$A = \text{number of protons} + \text{number of neutrons}$$

Question 1

Which statement from Dalton’s atomic theory has been disproven by modern science?

Accepted Answer

Atoms of one element cannot change into atoms of another element.

Question 2

Marie Curie’s work on radioactivity provided evidence that:

Accepted Answer

Atoms are made of smaller particles.

Question 3

Which experiment demonstrated the existence of the electron?

Accepted Answer

Thompson’s cathode ray experiment

Question 4

In Thompson’s cathode ray experiment, what property of the cathode ray led to the conclusion that it was made of electrons?

Accepted Answer

It was deflected by electric and magnetic fields.

Question 5

Which of the following is NOT a property of the particles in the cathode ray as discovered by Thompson?

Accepted Answer

They have high mass.

Question 6

Millikan’s oil drop experiment was designed to measure:

Accepted Answer

The charge of a single electron.

Question 7

Which formula correctly represents the force of gravity acting on a droplet in Millikan’s oil drop experiment?

Accepted Answer

$$F_{gravity} = m 	imes g$$

Question 8

Rutherford’s gold foil experiment led to which major conclusion about atomic structure?

Accepted Answer

Atoms contain a small, dense nucleus.

Question 9

Which model of the atom was disproven by Rutherford’s gold foil experiment?

Accepted Answer

Plum pudding model

Question 10

What is the atomic number ($$Z) of an $$element?

Accepted Answer

The number of protons in the nucleus

Question 11

Isotopes of an element have:

Accepted Answer

The same atomic number but different mass numbers

Question 12

How many neutrons are in an atom of Nitrogen-15?

Accepted Answer

8

Question 13

Which formula gives the mass number ($$A) of an $$atom?

Accepted Answer

$$A = 	ext{number of protons} + 	ext{number of neutrons}$$

Question 14

Which isotope notation correctly represents an isotope of Boron with 5 protons and 6 neutrons?

Accepted Answer

$$^{11}_{5}B$$

Question 15

Which hydrogen isotope is radioactive?

Accepted Answer

Tritium

Question 16

The atomic mass unit (amu) is defined based on which isotope?

Accepted Answer

Carbon-12

Question 17

The atomic weight of an element is:

Accepted Answer

A weighted average of the masses of its naturally occurring isotopes

Question 18

Given Boron is 20.0% $$^{10}B (10.0129 $$amu) and 80.0% $$^{11}B (11.0093 $$amu), what is its atomic weight?

Accepted Answer

$$10.8$$ amu

Question 19

Copper has two stable isotopes, Cu-63 (62.929599 u) and Cu-65 (64.927793 u). If the atomic mass of copper is 63.546 u, what is the fractional abundance of Cu-63?

Accepted Answer

$$0.69152$$

Question 20

Which of the following is NOT true regarding Fe-56?

Accepted Answer

Mass number of Fe-56 is 55.845

Foundations of Atomic Theory: Dalton, Radioactivity, and the Electron

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