Atomic theory 1 + 2 = Definitions, etc.

ELEMENT

substance that cannot be broken down into simpler substances by chemical means or produced by combining simpler substances

Group one is also called ?

alkali metals

group two is also called

alkali earth metals

group 7

halogens

group 8

noble gasses

properties of alkali metals

extremely reactive

soft metals

low densities

shine when freshly cut but tarnish rapidly due to reaction with air

stored under oil

burn in air to form the metal oxide

react vigorously with water to form metal hydroxide and hydrogen gas

Metal + oxygen gas =

metal oxide

Reactive metal + water =

metal hydroxide + hydrogen gas

ALKALINE EARTH METALS

very reactive but less reactive than the alkali metals

magnesium reacts slowly with water

HALOGENS

very reactive non-metals / low melting and boiling points

flourine and chlorine colour?

flourine and chlorine are yellow-green gases

bromine colour

red liquid

iodine at room temp is

a dark solid

NOBLE GASES

gaseous at room temp

boiling point increases down group

least reactive of all elements

Atoms

single neutral units

molecules

consist of two or more atoms bonded together

ions

are either single units or groups with a charge

MASS NUMBER (not in the periodic table) defn

number of protons plus neutrons in the nucleus of an atom

ATOMIC NUMBER Defn

the number of protons present in the nucleus of an atom

METAL Defn

any element that loses electrons to form a positive ion (cation)

ISOTOPES Defn

isotopes are atoms of the same element that have the same atomic number but different mass numbers due to the different numbers of neutrons present in the nucleus

RELATIVE ATOMIC MASS NUMBER (Ar) Defn

the average mass of an atom of an element compared to 1/12 the mass of the carbon – 12 isotope, taking relative abundances of the naturally occurring isotopes into account

RELATIVE MOLECULAR MASS NUMBER (Mr) defn

the average mass of a molecule of a compound compared to 1/12 the mass of the carbon – 12 isotope, taking relative abundancies of the naturally occurring isotopes into account

METAL + OXYGEN=

METAL OXIDE

METAL* + WATER

METAL HYDROXIDE + HYDROGEN GAS

AN ELEMENT Defn

substance that cannot be reduced to other simpler substances by chemical means or produced by combining simpler substances

THE OCTET RULE defn

states that when atoms bond atoms tend to want an electron arrangement of eight electrons in their outermost shell

VALENCY Defn

number of chemical bonds an atom can form

Carbon dioxide

one carbon to TWO (di) oxygens

Carbon monoxide

one carbon one oxygyn