Chemistry - Year 8

Protons are..

positively charged particles within the nucleus

Neutrons are…

neutrally charged particles ( no charge ) within the nucleus.

Electrons are..

negatively charged particles found ORBITING the nucleus.

Atoms have _ charge

Atoms have ZERO charge as they are balanced by a certain amount of protons, neutrons and electrons.

Ionization

the process of adding or removing electrons from an atom or molecule, which gives the atom or molecule a net charge ( rather than zero charge, it may have positive or negative )

Atomic Number

the number of protons in the nucleus of an atom, which is characteristic of a chemical element and determines its place in the periodic table.

Protons need __ to stabilise them.

Protons need NEUTRONS to stabilise them.

Atomic Mass

the total mass of particles of matter in an atom, i.e., the masses of protons, neutrons, and electrons in an atom added together.

Molecule

a group of two or more atoms that stick (bond) together. They can be pure elements or compounds. It is the simplest structural unit of an element or compound.

Elements

any substance that cannot be broken down into simpler substances. each element is made of its own kind of atom. e.g: carbon only contains carbon atoms.

Compounds

substances where the atom(s) of one element are BONDED to the atom(s) of another element, more simply known as different types of elements joined together.

Mixture

made up of two or more elements, two or more compounds or a combination of elements and compounds; but they ARE NOT all bonded together

Pure Substance

a single substance made of only one type of particle. e.g: Gold

Difference between Molecule & Compound

A molecule is a group of two or more atoms held together by chemical bonds. A compound is a substance formed by the chemical combination of two or more different elements. All compounds are molecules, but not all molecules are compounds.

Physical Change

change in a substance that does not create new product, is easily reversible and does not impact bonds or atoms.

Chemical Change

change in a substance that produces one or more new substances, chemical bond impacted and is not easily reversible.

Reaction Rate

a measure of how quickly a chemical reaction occurs

What can slow down a reaction?

lowering the temperature can slow down a chemical reaction.

What can speed up a reaction?

heating the temperature usually causes the rate of a reaction to increase.

Properties of a 𝘵𝘺𝘱𝘪𝘤𝘢𝘭 non-metal

• dull

• low density

• poor conductor of electricity & thermal energy

Properties of a 𝘵𝘺𝘱𝘪𝘤𝘢𝘭 metal

• good conductor of electricity & thermal energy

• high density

• malleable ( can be hammered into shapes )

• shiny

• can be drawn into wires

Why does metal conduct electricity?

The electrons are free to move about the metals lattice structure, conducting electricity.

Exothermic Reactions

Chemical reactions that release a significant amount of heat & energy.

Catalyst in a chemical reaction

a catalyst is a chemical that can speed up a chemical reaction but is not used in the reaction.

relationship between protons and electrons

number of protons = number of electrons *in a element without ionization

Noble Gases

elements in group 18 that are known for their low chemical reactivity, meaning they are generally unreactive with other elements

Ions

when an atom will gain/lose electrons to achieve a stable outer shell

Anion

negative charge ions

Cation

positive charge ions

Valence Electrons

electrons in the outermost shell of an atom

a element's group dictates its…

-valence electrons, group 7 = 7 valence electrons

a element's period dictates

• how much electron shells it has, period 3 = 3 electron shells

What type of bond occurs between metals?

Metallic bonds, characterized by shared moving electrons.

What type of bond occurs between metals and non-metals?

Ionic bonds, where electrons are transferred between atoms.

What type of bond occurs between non-metals?

Covalent bonds, where electrons are shared.

What is valency?

The number of electrons an atom can lose, gain, or share to achieve a stable electron configuration.

What is the significance of valence electrons?

They are the electrons available for bonding and reactions. An atom's tendency to form chemical bonds with other atoms is directly related to the number and arrangement of its valence electrons.