Question 1

Which experiment provided the first evidence for the existence of negatively charged subatomic particles, and what was the key observation?

Accepted Answer

Thomson's Cathode Ray Tube Experiment; cathode rays were deflected by electric and magnetic fields

Question 2

According to Dalton's Atomic Theory, which statement is INCORRECT based on modern atomic understanding?

Accepted Answer

Atoms of a given element are identical in mass and properties

Question 3

A sample of magnesium contains two naturally occurring isotopes: $$^{24}Mg (78.99$$%, mass = 23.985 amu) and $$^{26}Mg (11.01$$%, mass = 25.983 amu). What is the average atomic mass of magnesium?

Accepted Answer

$$24.31$$ amu

Question 4

Which law states that the ratio of the masses of one element that combine with a fixed mass of another element in different compounds is a simple whole number?

Accepted Answer

Law of Multiple Proportions

Question 5

A neutral atom of chlorine has an atomic number $$Z = 17$$ and a mass number $$A = 35. $$How many neutrons does it contain?

Accepted Answer

$$18$$

Question 6

Which statement best describes the result of Rutherford's Gold Foil Experiment?

Accepted Answer

Most of the atom's mass is concentrated in a small, dense nucleus

Question 7

Which of the following ions has the same number of electrons as a neon atom ($$Z = 10$$)?

Accepted Answer

$$Na^+$$

Question 8

A compound contains 40.0 g of carbon and 53.3 g of oxygen. What is the mass fraction of carbon in the compound?

Accepted Answer

$$0.429$$

Question 9

Which statement about isotopes is TRUE?

Accepted Answer

Isotopes of the same element have the same chemical properties but different masses

Question 10

Which group on the periodic table contains elements that tend to gain electrons to achieve a noble gas configuration?

Accepted Answer

Halogens (Group 17)

Question 11

If a main group metal forms an ion, what is the expected charge of the ion?

Accepted Answer

Positive, equal to the number of electrons lost to achieve noble gas configuration

Question 12

Which of the following best describes the Law of Definite Proportions?

Accepted Answer

A compound always contains the same elements in the same proportion by mass

Question 13

A sample contains $$3.01 	imes 10$$^{23}$$ atoms of carbon. How many moles of carbon are present?

Accepted Answer

$$0.500$$ mol

Question 14

Which statement about the periodic law is correct?

Accepted Answer

When elements are arranged by increasing atomic mass, certain sets of properties recur periodically

Question 15

Which of the following is a correct representation of the atomic number ($$Z) $$and mass number ($$A) $$for an atom with 15 protons and 16 neutrons?

Accepted Answer

$$Z = 15$$, $$A = 31$$

Question 16

Which of the following statements about ions is TRUE?

Accepted Answer

Cations have fewer electrons than protons

Question 17

A chemical reaction occurs in a closed system. The total mass of reactants is 50.0 g. What will be the total mass of products according to the Law of Conservation of Mass?

Accepted Answer

50.0 g

Question 18

Which scientist is credited with the discovery of the electron?

Accepted Answer

J.J. Thomson

Question 19

Which of the following best explains why atoms of the same element can have different masses?

Accepted Answer

They have different numbers of neutrons

Question 20

A main group nonmetal forms an ion with a $$2-$$ charge. How many electrons does this ion have compared to its neutral atom?

Accepted Answer

Two more electrons

chapter 2

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