Unit 3 Test Review

Front

Atoms of elements in the same group of the periodic table share the same.

Back

number of valence electrons

Answer explanation

Atoms in the same group of the periodic table have the same number of valence electrons, which determines their chemical properties. This is why elements in a group behave similarly in reactions.

Front

What is an atom’s nucleus made of?

Back

protons and neutrons

Answer explanation

An atom's nucleus is composed of protons and neutrons. Protons carry a positive charge, while neutrons are neutral. Electrons, which are negatively charged, orbit the nucleus but are not part of it.

Front

How many electrons will a neutral atom of carbon have if its nucleus has 6 protons and 8 neutrons?

Back

6

Answer explanation

A neutral atom has an equal number of protons and electrons. Since the carbon nucleus has 6 protons, it will also have 6 electrons, making the correct answer 6.

Front

An element with 5 protons, 6 neutrons, and 8 electrons has an atomic number of

Back

5

Answer explanation

The atomic number of an element is defined by the number of protons it has. Since this element has 5 protons, its atomic number is 5.

Front

Mass number of an element with 5 protons, 6 neutrons, and 8 electrons?

Back

11

Answer explanation

The mass number A is the sum of protons and neutrons. Here, there are 5 protons and 6 neutrons, so A = 5 + 6 = 11. The number of electrons does not affect the mass number.

Front

The farther an electron is from the nucleus, the more ________ it has.

Back

energy

Answer explanation

The farther an electron is from the nucleus, the more energy it possesses. This is because electrons in higher energy levels are less tightly bound to the nucleus, allowing them to have greater energy compared to those closer to the nucleus.

Front

Atoms of the same element that have different numbers of neutrons are called

Back

isotopes

Answer explanation

Atoms of the same element with different numbers of neutrons are called isotopes. They have the same number of protons but vary in mass due to the differing neutron count, distinguishing them from molecules, ions, and protons.

Front

The total number of electrons in the outer shell of a sodium atom is

Back

1

Answer explanation

A sodium atom has 11 electrons, with 1 electron in its outer shell (valence shell). This makes the correct answer 1, as sodium is in group 1 of the periodic table.

Front

Which particles determine the atomic number of an element?

Back

Protons only

Answer explanation

The atomic number of an element is determined solely by the number of protons in its nucleus. Neutrons and electrons do not affect the atomic number, making 'Protons only' the correct choice.

Front

The total number of neutrons in the nucleus of any atom is equal to the

Back

mass number minus the atomic number

Answer explanation

The total number of neutrons in an atom is calculated by subtracting the atomic number (number of protons) from the mass number (total protons and neutrons). Thus, neutrons = mass number - atomic number.