$$(0.7577 \times 34.97) + (0.2423 \times 36.97) = 35.45$$ amu

Question 1

Which statement best summarizes Dalton’s atomic theory as it relates to the composition of water (H$$_2O$$)?

Accepted Answer

Water is composed of hydrogen and oxygen atoms that are chemically bonded in a 2:1 ratio.

Question 2

Which experimental result led Rutherford to propose the nuclear model of the atom?

Accepted Answer

A small fraction of alpha particles were deflected at large angles when passing through gold foil.

Question 3

Which of the following statements about subatomic particles is correct?

Accepted Answer

Protons and neutrons are found in the nucleus, while electrons are found outside the nucleus.

Question 4

Which element is represented by the chemical symbol 'K' and what is its atomic number?

Accepted Answer

Potassium, atomic number 19

Question 5

Which of the following best describes the difference between metals, nonmetals, and metalloids?

Accepted Answer

Metals are good conductors, nonmetals are poor conductors, and metalloids have intermediate conductivity.

Question 6

A magnesium ion has 10 electrons. What is its charge and how is it represented?

Accepted Answer

$$\mathrm{Mg$$^{2+}$$}$$

Question 7

Which group in the periodic table contains elements that are chemically inert and rarely form compounds?

Accepted Answer

Group 8A (Noble gases)

Question 8

How many protons, neutrons, and electrons are present in a neutral atom of $$^{10}\mathrm{B} ($$boron-10)?

Accepted Answer

5 protons, 5 neutrons, 5 electrons

Question 9

Which of the following ions is an anion?

Accepted Answer

$$\mathrm{Cl$$^{-}$$}$$

Question 10

Which property is shared by all isotopes of a given element?

Accepted Answer

They have the same number of protons.

Question 11

Calculate the average atomic mass of chlorine given that it consists of 75.77% chlorine-35 (mass 34.97 amu) and 24.23% chlorine-37 (mass 36.97 amu).

Accepted Answer

$$(0.7577 	imes 34.97) + (0.2423 	imes 36.97) = 35.45$$ amu

Question 12

Which of the following best explains why atoms are electrically neutral?

Accepted Answer

The number of protons equals the number of electrons.

Question 13

Which element is a metalloid and is commonly used in the electronics industry as a semiconductor?

Accepted Answer

Silicon (Si)

Question 14

Which of the following elements is a halogen?

Accepted Answer

Bromine (Br)

Question 15

A sulfur ion has 18 electrons. What is its charge and how is it represented?

Accepted Answer

$$\mathrm{S$$^{2-}$$}$$

Question 16

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

Accepted Answer

Elements in the same group have similar chemical properties.

Question 17

Which of the following is the correct isotope symbol for a neon atom with 10 protons and 12 neutrons?

Accepted Answer

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

Question 18

Which of the following best describes the trend in reactivity for alkali metals (Group 1A) as you move down the group?

Accepted Answer

Reactivity increases as you move down the group.

Question 19

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

Accepted Answer

Atomic number = 17, mass number = 35, symbol = Cl

Atoms and Elements: Structured Study Notes for Introductory Chemistry

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