35 terms

Terms	Definitions
matter	Anything that occupies space and has mass
element	A pure substance containing atoms of only one type e.g. pure copper metal (Cu) contains only atoms of copper.
compound	A substance containing two or more elements chemically combined in a fixed ratio e.g. water has the formula H₂O
atom	The smallest component of an element having the chemical properties of the element.
proton	A subatomic particle having a positive charge and found in the nucleus
electron	A subatomic particle having a negative charge and relatively no mass which is not found in the nucleus.
neutron	A subatomic particle without a charge and found in nucleus.
nucleus	The part of the atom where nearly all its mass is concentrated.
atomic number	It equals the number of protons in the nucleus of the atom of each element.
isotope	Atoms having the same numbers of protons but different numbers of neutrons.
ion	Charged atoms that have lost or gained electrons.
ionic bond	Occurs when atoms transfer electrons to other atoms thus becoming charged and are consequently attracted to each other.
covalent bond	Occurs when atoms share electrons and
molecule	Groups of atoms that are held together by covalent bonds.
chemical reaction	The interaction of substances that lead to the formation of new substances.
reactant	The starting materials for a reaction; found on left side of chemical equation
product	The ending materials of a reaction; found on right side of chemical equation
organic compound	A substance made of two or more elements, one being carbon
inorganic compound	substance made of two or more elements, none of which is carbon
valence electrons	Electrons in the outermost energy level; they are involved in bond formation.
single bond	a covalent bond in which one pair of electrons is shared
double bond	a covalent bond in which four valence electrons are shared between two atoms
chemical formula	indicates the number and types of atoms in a molecule
structural formula	shows the number and types of atoms in a molecule and how they are arranged
chemical reaction	indicates the formation of new substances from previous substances
electron shells	Levels of electrons around the nucleus. Each level can accommodate a specific number of electrons. The outermost levels have the highest energy.
ground state	A state in which all the electrons in an atom have the lowest possible energies.
electron configuration	The arrangement of electrons in a neutral atom when in its ground state.
periodic table	A table that shows the elements, their atomic number, symbol, and average atomic mass; elements with similar chemical properties are grouped together.
metal	A substance that is malleable, ductile has a lusture and conducts heat and electricity.
non - metal	An element that is usually a gas or solid at room temperature, is not malleable or ductile, is a poor conductor of heat and electricity, and is typically not shiny.
periods	Horizontal rows on the periodic table - all elements in each row have the same number of electron shells. The maximum number of electrons each shell can hold equals 2n² where n equals the row number or quantum level.
groups	Columns in periodic table; also known as "families"; elements in same "families" have similar physical and chemical properties because they have the same number of valence electrons in their outer electron shells or orbitals.
Dmitri Ivanovich Mendeleev born 1834 died 1907	Russian chemist who developed a periodic table of the chemical elements based on their atomic mass and similarity of properties. He predicted the discovery of several new elements.
Henry Gwyn Jeffreys Moseley born 23 November 1887 died 10 August 1915	Brillant English physicist who revised Mendeleev's periodic table; ordered the elements based on atomic number rather than weigth. Tragically killed while serving with the British army in Gallipoli during World War 1.

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