Chemistry Class Review

How many elements are on the Periodic Table?

• 18

• 50

• 51

• 118

Answer explanation

The periodic table, which organizes chemical elements based on their atomic number, electron configuration, and recurring properties, consists of 118 known elements. So, the correct answer to the question 'How many elements are on the Periodic Table?' is 118.

What is the chemical symbol for the element Sodium?

• S

• 11

• So

• Na

Answer explanation

The chemical symbol for the element Sodium is 'Na'. This is derived from the Latin name for sodium carbonate, 'natrium'. So, the correct option among the given ones is 'Na'.

Which of the following descriptions goes with Nonmetals?

• Mostly solid at room temperature. Shiny. Good conductors.

• Mostly gases at room temperature. Poor conductors.

• Sometimes gases, sometimes solids are room temperature. Semiconductors

• Sometimes gases. Great conductors. Very shiny.

Answer explanation

The question asks for the description that matches Nonmetals. The correct answer is 'Mostly gases at room temperature. Poor conductors.' This is because nonmetals, unlike metals, are poor conductors of heat and electricity and are primarily in gaseous state at room temperature.

Where are electrons located in atoms?

• Nucleus

• Electron Areas

• Electron Orbitals

• Isotopes

Answer explanation

Electrons in atoms are located in areas known as electron orbitals. These are not physical locations, but rather probability areas where an electron can be found. The other options, such as the nucleus and isotopes, relate to different parts of an atom or atomic variations, while 'electron areas' is not a specific term in atomic structure.

Where are protons located in atoms?

• Nucleus

• Electron Areas

• Electron Orbitals

• Isotopes

Answer explanation

Protons are located in the nucleus of an atom. In atomic structure, the nucleus is the central part of the atom that contains both protons and neutrons. The other options like Electron Areas, Electron Orbitals and Isotopes do not refer to the location of protons within an atom.

Where are neutrons located in atoms?

• Nucleus

• Electron Areas

• Electron Orbitals

• Isotopes

Answer explanation

Neutrons, together with protons, make up the nucleus of an atom. The nucleus is the central part of the atom. The other options, such as electron areas or electron orbitals, are where electrons reside, not neutrons. And isotopes are variants of a particular chemical element which differ in neutron number, not a location in an atom.

If an atom of Carbon is neutral, how many electrons does it have?

• 4

• 5

• 6

• 8

Answer explanation

In a neutral atom, the number of electrons equals the number of protons. Carbon, being the sixth element on the periodic table, has 6 protons. Therefore, a neutral carbon atom also has 6 electrons, thereby making the correct choice 6.

If an atom of Helium is neutral, how many electrons does it have?

• 2

• 4

• 1

• 3

Answer explanation

A neutral atom of any element, including Helium, has the same number of electrons as protons. Helium has 2 protons in its nucleus. Therefore, a neutral Helium atom must also have 2 electrons. This matches with the correct answer provided.

If an atom of Fluorine has a -1 charge, it:

• Is an anion. It has more electrons than protons.

• Is an anion. It has more protons than electrons.

• is a cation. It has more electrons than protons.

• is a cation. It has more protons than electrons.

Answer explanation

The question asks about the charge of a Fluorine atom with a -1 charge. The correct response 'Is an anion. It has more electrons than protons.' is due to the fact that an atom becomes an anion when it gains electrons, leading to a negative charge. In this case, the Fluorine atom has one extra electron, giving it a -1 charge, thus it has more electrons than protons.

If an atom of Calcium has a +2 charge, how many electrons does it have?

• 2

• 20

• 18

• 22

Answer explanation

An atom of Calcium normally has 20 electrons. If it has a +2 charge, it means it has lost 2 electrons. Hence, the total number of electrons left would be 20-2 = 18. So, the correct answer is 18.