Q: What is the formula for calculating the average atomic mass of an element?

$\mathrm{AM} = \sum [(\text{isotope mass}) \times (\text{fractional abundance})]$

Question 1

Which experiment led to the discovery of the atomic nucleus?

Accepted Answer

Ernest Rutherford's gold foil experiment

Question 2

What is the charge and relative mass of a neutron?

Accepted Answer

Charge: $0$, Mass: $1.0087$ amu

Question 3

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes have different numbers of neutrons but the same number of protons.

Question 4

Calculate the atomic mass of gallium given the following data: $^{69}\mathrm{Ga}$ (isotopic mass $= 68.9256$ amu, $60.11\%$) and $^{71}\mathrm{Ga}$ (isotopic mass $= 70.9247$ amu, $39.89\%$).

Accepted Answer

$69.72$ amu

Question 5

Which type of radiation discovered by Rutherford is uncharged?

Accepted Answer

$\gamma$ rays

Question 6

What is the atomic number and what does it represent?

Accepted Answer

The number of protons in the nucleus

Question 7

A neutral atom of potassium ($K$) has an atomic number of $19$. How many electrons does it have?

Accepted Answer

$19$

Question 8

Which group on the periodic table is known for forming 1- ions?

Accepted Answer

Halogens (Group 7A)

Question 9

What is the formula for calculating the average atomic mass of an element?

Accepted Answer

$\mathrm{AM} = \sum [(	ext{isotope mass}) 	imes (	ext{fractional abundance})]$

Question 10

Which property is NOT characteristic of metals?

Accepted Answer

Forming 1- ions

Question 11

How many electrons are present in the $\mathrm{O}^{2-}$ anion?

Accepted Answer

$10$

Question 12

Which statement best describes the periodic law?

Accepted Answer

When elements are arranged in order of increasing mass, certain sets of properties recur periodically.

Question 13

Which of the following elements is a metalloid?

Accepted Answer

Silicon

Question 14

A main-group metal tends to lose electrons and form a cation with the same number of electrons as:

Accepted Answer

The nearest noble gas

Question 15

Which of the following is the correct symbol for an isotope of neon with 12 neutrons?

Accepted Answer

$^{22}_{10}\mathrm{Ne}$

Question 16

Which element is part of the group known for their salt-forming ability?

Accepted Answer

Halogens

Question 17

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

Accepted Answer

$35$

Question 18

Which of the following statements about the 'plum pudding' model is correct?

Accepted Answer

It describes the atom as a positive sphere with electrons embedded throughout.

Question 19

Which group on the periodic table tends to gain two electrons and form $2-$ ions?

Accepted Answer

Chalcogens (Group 6A)

Question 20

Which instrument is used to measure atomic and molecular masses and determine isotopic abundances?

Accepted Answer

Mass spectrometer

Atoms, Molecules, and Ions: Structure, Properties, and the Periodic Table

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