Chemistry - Key terms - Grade 9

key terms needed for grade 9 chemistry

definition of monotomic

exist as one atom and is happy, can be found alone in nature

definition of diatomic

never are alone in nature - most halogens

definition of (good)conductors

a material that transmits heat and electricity.

definition of malleable

a material that are able to be hammered or pressed into a shape without breaking

definition of ductile

a material that is able to be drawn into a thin wire

definition of Lustre

a gentle sheen or glow. often described as shiny.

definition of cations

a positively charged ion

definition of anion

a negatively charged ion

definition of brittle

hard but easy to break

what does Z_eff stand for

effective nuclear charge

what does Z stand for

number of protons

what does S stand for

number of inner electrons

How to calculate the effective nuclear charge

Z_eff = Z-S

why do atoms get more reactive, the further down the group you go?

Valence e- are further away from the nucleus and therefore don’t feel the positive charge as much

superscript

tells the charge of the ion

Element

A pure substance that is made up of only one atom

Atom

Smallest particle of an element

Molecule

chemically bonded atoms that can be the same or different

compound

two or more different chemically bonded atoms

cation

positively charged ions(metals)

Ion dot diagram must have brackets, charge and 0 electron dots around it

aniona

negatively charged ions(nonmetals)

Ion dot diagram brackets, charge and 8 dots around the ion

electrostatic force

the force between two electrically charged objects

hold metallic and covalent bonds

ionic bond

a bond between metal and non metal that exchange electrons, creating two full octets

electrostatic attraction between cations and anions

the form energy is _

released(exothermic)

Remember: BARF = BreakAbsorb ReleaseForm

To break bonds energy is _

absorbed (endothermic)

Remember: BARF = BreakAbsorb ReleaseForm

ionic Properties

Conduct: (l) and (aq) phase not (s)

Dissociate in water

MP & BP: High

Brittle

Neutral Charge

Form crystal lattice

Metalic Properties

Conduct: always

MP & BP: High

Malleable & ductile

Form crystal lattice - compact & ordered

Covalent Proteries

Conduct: never

MP & BP: Low

Neutral Charge

Can be polar or non-pola

Alloy

A mixture of two or more elements ( at least 1 being a metal). Has properties that are superior to its components.

ex) Steel & brass

single bonds are made of _

a covalent bond between two atoms sharing one pair of electrons (a.k.a two electrons)

double bonds are made of _

a covalent bond between two atoms sharing two pairs of electrons (a.k.a four electrons)

tripple bonds are made of _

a covalent bond between two atoms sharing three pairs of electrons (a.k.a six electrons)

shared pair

ny bonding pair of electrons shared between 2 atoms

lone pair

any non-bonding (unshared) pairs of electrons around an atom in a molecule but notbetween that atom and another