chemical bond
the attractive force that holds atoms or ions together
chemical symbol
one or two letter representation of an element
chemical formula
a combination of chemical symbols and numbers to represent a substance
ion
atom that has a positive or negative charge because it lost or gained one or more electrons
ionic bond
a chemical bond in which one atom loses an electron and the other atom gains electrons to form ions, formed between a cation and an anion. An atom that prefers to lose electrons will often form a bond with an atom that prefers to gain electrons. A very st
anion
An ion with an overall negative charge because it gained one or more electrons. Anions are usually nonmetals found on the right side of the periodic table. Flourine likes to gain electrons.
cation
a positively charged atom with fewer electrons than protons. Cations are usually metals, found on the left side of the periodic table.
compound
A substance made up of atoms of two or more different elements joined by chemical bonds
energy level
A particular region where electrons can orbit a nucleus. (electron cloud)
group
columns; shared chemical properties; representative element groups tell # of valence electrons
Noble gas
Elements in group 18 (8A) of the periodic table; NOT reactive because full valence electron levels
Halogen
Group 17 (7A)Contains nonmetals, 7 valence electrons; Very reactive.
Alkali metal
Group 1A; charge of +1; reacts with the halogens to form compounds. Ex. NaCl.
valence electrons
the electrons in the highest occupied energy level of an atom. The number of valence electrons mostly determines the properties of an element. On periodic table groups 1-8, signify atoms that have 1-8 valence electrons. All atoms want 8 electrons only in
octet rule
atoms like to have full outer shells of only eight electrons. Atoms will lose or gain valence electrons to make their outer shells full with eight electrons, and they do this by bonding with other atoms. exceptions to the octet rule are hydrogen and heliu
intramolecular bonding
bonds that occur between atoms within the same molecule.
Hydrogen Bonding
one of the major intermolecular bonds that plays a significant role in biology. hydrogen atoms are going to spend more time being positive than the oxygen atom, which has a larger electronegativity, so that's drawing the electrons a little bit more toward
law of conservation of energy
states that in any chemical or physical process, energy is neither created nor destroyed, so if energy of the system decreases, then the energy of the surroundings increases by the same amount.
exothermic reaction
If heat is given off, the reaction is exothermic. Exothermic means that during the reaction, molecules have moved from a higher state of energy to a lower state. A bond is made.
endothermic reaction
This is when a reaction starts colder and ends up hotter, taking in energy from start to finish. A bond is broken.
metal bonding
metals are made up of closely packed cations that are surrounded by a mobile sea of valence electrons
alloy
a combination; a mixture of elements, one of which must be a metal. It is usually 2 or more metals.
substitutional alloy
Metal atoms replaced by metal atoms of same size
interstitial alloy
formed when the small holes in a metallic crystal are filled with smaller atoms
ductile
can be drawn into wires
malleable
capable of being shaped
Metal properties
good conductors of heat and electricity; malleable; solid at room temp; more dense than water; ductile; have luster
simple cube
Simplest arrangement of atoms in a crystalline structure.
body-centered cube
a unit cell that consists of a cube with one atom at each corner and one atom at the center of the cube
face-centered cube
every atom has 12 neighbors
(example: Cu, Ag, Au, Al, Pb)