Science Grade 7: Chemistry

Question 1

What is the atomic number of an atom?

Answer 1

The number of protons in an atom is called its atomic number. This is unique for each element, so it is a way of telling elements apart.

Question 2

What is the atomic mass?

Answer 2

An atom’s mass number is its mass in atomic mass units (amu), which is about equal to the total number of protons and neutrons in the atom. Different isotopes of an element have different mass numbers because they have different numbers of neutrons.

Question 3

How can the atomic number and the atomic mass of an atom be told apart?

Answer 3

The atomic number is always less than the atomic mass.

Question 4

What are isotopes?

Answer 4

All atoms of the same element have the same number of protons, but some may have different numbers of neutrons. Atoms of the same element that differ in their number of neutrons are called isotopes.

Question 5

Why are atoms neutral in electric charge?

Answer 5

Atoms have equal numbers of positive protons and negative electrons, so they are neutral in electric charge.

Question 6

What is an ion?

Answer 6

Atoms can gain or lose electrons and become ions, which are atoms that have a positive or negative charge because they have unequal numbers of protons and electrons.

Question 7

What is a cation?

Answer 7

A cation is an ion of an atom with positive charge, so they have more protons than electrons.

Question 8

What is an anion?

Answer 8

An anion is an ion of an atom with negative charge, so they have more electrons than protons.

Question 9

How do ions form?

Answer 9

The process in which an atoms becomes an ion is called ionization. It may occur when atoms are exposed to high levels of radiation or when atoms transfer electrons to or from other atoms.

Question 10

What are the properties of ions?

Answer 10

• Reactive
• Attracted or repulsed by other charged particles
• Deflected by a magnetic field

Question 11

Why is the atomic nucleus very dense?

Answer 11

The nucleus is just a tiny part of the atom, but it contains virtually all of the atom’s mass.

Question 12

How big is the atomic nucleus?

Answer 12

The radius of the nucleus is only about 1/100,000 of the total radius of the atom.

Question 13

What is a proton?

Answer 13

A proton is one of the three main particles that make up the atom. It is found in the nucleus. It has an electrical charge of +1 and a mass of 1 atomic mass unit (amu)

Question 14

What is the relationship between protons and elements?

Answer 14

Atoms of any given element have a unique number of protons that is different from the number of protons of all other elements.

Question 15

Why is the nucleus positive in charge?

Answer 15

The nucleus consists of positive protons and neutral neutrons, so it has an overall positive charge.

Question 16

What is a neutron?

Answer 16

A neutron is one of the three main particles that make up the atom. It is found in the nucleus and is neutral in electric charge.

Question 17

What are electrons?

Answer 17

Electrons are one of the three main particles that make up the atom. They are extremely small and have an electric charge of -1.

Question 18

What is the difference between electrons and protons?

Answer 18

All atoms have the same number of protons as electrons (ions are an exception). While protons have an electric charge of +1, electrons have an electric charge of -1. Furthermore, protons are found in the nucleus while electrons orbit around the nucleus

Question 19

What are valence electrons?

Answer 19

Electrons at the outermost energy level of an atom are called valence electrons. They are important because they determine many of the properties of an element. That’s because these electrons are involved in chemical reactions with other atoms.

Question 20

What are molecules?

Answer 20

Molecules are the smallest units formed when atoms combine with each other.

Question 21

What are compounds?

Answer 21

Compounds contain atoms of two or more elements held together by chemical bonds.

Question 22

What is the basic law of conservation of mass?

Answer 22

In chemical reactions, mass is neither created nor destroyed.

Question 23

What is the rule of compounds?

Answer 23

Element + Element = Compound

Question 24

How do the properties of compounds compare with the properties of the elements that form them?

Answer 24

The properties of compounds may be very different from the properties of the elements that form them.

Question 25

What are crystals vs molecules?

Answer 25

Some compounds form rigid frameworks called crystals. Other compounds form individual molecules. A molecule is the smallest particle of a compound that still has the compound’s properties.

Question 26

What is an element?

Answer 26

An element is a pure substance that cannot be seperated into any other substances.

Question 27

Why can an element be identified by its properties?

Answer 27

Each element has a unique set of properties that is different from the set of properties of any other element.

Question 28

How are atoms related to elements?

Answer 28

The smallest particle of an element that still has the properties of that element is the atom. All the atoms of an element are like one another, and are different from the atoms of all other elements.

Question 29

What are the groups of the periodic table?

Answer 29

A groups of the periodic table is a vertical column. Each group has the same number of electrons on the last shell.

Question 30

What are the periods of the periodic table?

Answer 30

A period of the periodic table is a horizontal row. Each period has the same number of shells.

Question 31

What are metals?

Answer 31

Metals are elements that can conduct electricity. Most elements are metals.

Question 32

What are some properties of metals?

Answer 32

All metals except for mercury are solids at room temperature. Many metals are shiny, ductile, and malleable. Most are also good conductors for heat.

Question 33

What are non-metals?

Answer 33

Non-metals are elements that generally cannot conduct electricity. They are the second largest class of elements after metals. Examples of nonmetals include hydrogen, carbon, chlorine, and helium.

Question 34

Why do non-metals vary in their reactivity?

Answer 34

Some non-metals are very reactive, whereas others are not reactive at all. It depends on the number of electrons in their outer energy level / shell.

Question 35

What are metalloids?

Answer 35

Metalloids are the smallest class of elements, containing just six elements. They fall between metals and non-metals in the periodic table.

Question 36

What properties do metalloids share with both metals and non-metals?

Answer 36

Most metalloids have some physical properties of metals and some physical properties of non-metals. They fall between metals and non-metals in their ability to conduct heat and electricity

Question 37

What properties do metalloids share only with metals?

Answer 37

The only physical property that only metalloids and metals share is that they are shiny.

Question 38

What is the difference between molecules and compounds?

Answer 38

A molecule is formed when two or more atoms of an element chemically join together. A compound is a type of molecule, in which the types of atoms forming the molecule are different from each other.