Review of Major Concepts Taught in Grade 9 Chemistry

Review of Major Concepts Taught in Grade 9 Chemistry

Review of Major Concepts Taught in Grade 9 Chemistry Structure of the Atom: An atom is made up of the following subatomic particles: o Protons - have a positive charge and are found inside the nucleus. A proton has a mass of 1 a.m.u. (atomic mass unit) o Neutrons - have no charge and are found inside the nucleus. A neutron has a mass of 1 a.m.u. o Electrons- have a negative charge and are found outside the nucleus in orbitals or shells . An electrons mass is 1/2000 of a proton or neutrons mass.

Determining the Number of Subatomic Particles: The atomic number of an element tells us how many electrons and protons it has. The atomic mass of an element is determined by adding the number of neutrons to the number of protons. Number of protons Number of electrons Number of neutrons

Atomic Mass Atomic Number Element Name Chemical Symbol 23 23

28 51 23 Vanadium V 12 12

12 24 12 Magnesium Mg 56 56 81

137 56 Barium Ba 45 30 Scandium

35 59 28 Bohr Models: The Bohr model of the atom represents the number of subatomic particles found in one atom of a certain element. When drawing a Bohr model, the nucleus is represented by a circle which contains the element symbol, the number of protons and the number of neutrons. The electrons are drawn in orbitals (also called electron shells or energy levels) outside of the nucleus. The first orbital can hold a maximum of 2 electrons. The

second orbital can hold a maximum of 8 electrons and the third orbital can hold a maximum of 8 electrons. Bohr Model for Fluorine Hydrogen Bohr Model Helium Bohr Model Magnesium Bohr Model Oxygen Bohr Model Valence Electrons:

Valence electrons are the electrons found in the outermost electron orbit or shell. An elements valence number provides information about what type of ion that element will form and how it will combine with other elements to form compounds. How many valence electrons do each of the following elements have? Flourine: ______________

Hydrogen: ______________ Helium: ______________ How many valence electrons do each of the following elements have? Magnesium: ______________

Oxygen: _______________ Periodic Table: The periodic table is an arrangement of elements based on increasing atomic mass. Elements are arranged into vertical columns called groups or families.

Elements are also arranged into horizontal rows called periods. Elements that are found in the same group or family share similar properties. Elements in the same group also have the same number of valence electrons.

Grab the following marker colours: Red Orange Yellow

Green Blue Purple Chemical Families: Hydrogen Family (RED) Contains only one element, Hydrogen.

Hydrogen has 1 valence electron that it either loses, gains or shares when bonding with other elements. This makes it unique. Alkali metals (ORANGE) Found in group 1 on the periodic table. Have 1 valence electron. Very reactive. Alkali metals tend to lose electrons when forming compounds. Alkaline Earth Metals (YELLOW) Found in group 2on the periodic table. Have 2 valence electrons. Alkaline Earth metals tend to lose electrons when forming compounds.

Chalcogens (GREEN) Found in group 6 on the periodic table. Have 6 valence electrons. Chalcogens tend to gain electrons when forming compounds. Halogens (BLUE) - Found in group 7 on the periodic table. Have 7valence electrons. Very reactive. Halogens tend to gain electrons when forming compounds. Noble Gases (PURPLE) - Found in group 8 on the periodic table. Have

8 valence electrons or a full outer shell. Noble Gases are considered inert which means they do not react.

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