chemical bonding Flashcards
definition of element
contains only 1 kind of atoms, cannot be broken down into simpler substances
define compound
2 or more atoms of different elements, chemically bonded together
define mixture
mixture contains different substances that are not bonded tgt
what are the 3 signs of chemical change
1) one or more new chemical substances are formed
2) energy is take in or given out
3) change is difficult to reverse
define physical change
when no new chemical substance is formed
in molecules and compounds, atoms are held tgt by _____
chemical bonds
why do atoms form bonds?
to gain a stable arrangement of outer shell electrons, like grp 8
makes them more chemically stable
what is valency
number of electrons an atoms uses for bonding
how many valency does iron(III) have
3 i think
what is ionic bonding?
the strong electrostatic force of attraction between oppositely- charge ions/ bond that forms between ions of opposite charge
do metal or non metals form an anion during ionic bonding?
non metals
true or false: the charge of ion does not reflect the number of electrons it has gained or lost.
false
what is group’s 1 ionic charge?
+1
what is groups 2 ionic charge
+2
true or false: the charge of ions does reflect the number of electrons it has gained or lost ?
true
what is group 3 ionic charge?
+3
what is the ionic charge for grp 7,6,5
-1,-2,-3
what is the pattern that is formed in ionic bond
lattice , alternating positive and negative ions
what are the 4 properties of ionic compounds
high m&b points, hard and brittle, soluble in water but insoluble in organic solvent , can conduct electricity in aqueous but not solid
does ionic compound have high or low melting points? why
high; strong EFOA holds the oppositely charged ions tgt in the lattice.
because the ionic bond is very strong, it takes a lot of heat to overcome these strong forces
can the ionic compounds conduct electricity? why or why not
solid cannot conduct electricity because in solid state, ions are vibrating at fixed position and do not move freely. but when it melts or dissolves in water to form a solution it can because the ions are moving freely. since the ions are charges, they can carry electrical charges and conduct electricity
is ionic compounds soluble in water? why or why not?
it is soluble in water because water molecules are able to separates the ions from each other. when the ions move apart, they will be surrounded by water molecules
does hydrogen lose or gain electrons
lose electrons to from positive ion
why do they element in grp 4 and 5 not form ions?
they wld hv to gain or lose several electrons and that’s takes up too much energy
why do grp 8 not form ions?
because they already have a stable outer shell, so they do not need to gain or loses electrons
true or false: some metals can form more than one type of ion.
true
what transitional metal forms more than 1 type of ion and which don’t
copper and iron ; zinc and silver
what are compound ions?
ions that are formed from a group of bonded atoms
what is a giant ionic structure
when ions are arranged in geometric 3D patterns which go one forever
true or false: all ionic compound do not have giant ionic structure
false
what is a crystalline structure
the regular arrangement of ions in the lattice
are ionic crystals brittle? why
yes, because once layer of ions in the crystals has been forced to move, ions of the same charge will be next to each other and will repel, splitting the crystal
what is metallic bond
strong EFOA between the metals cations and negative ‘sea’ of electrons tgt in a lattice
why does metal atoms get packed tightly tgt in a regular lattice?
to allow outer electrons separate from their atoms. results is a lattice of ions on a ‘sea’ of electrons that are free to move
what does the regular arrangement of ions results in?
crystals
physical properties of a metal?
high melting and boiling pints, conduct h&e, malleable and ductile and hard
why does metal conduct heat in solid and liquid
free electrons take in heat energy
move faster
quickly transfer heat though metal structure
why can metal conduct electricity
delocalized (removed) electrons move freely though the metal lattice to carry electrical charges
free electrons can move through the lattice carrying charge
why do metal have high melting and boiling point?
strong EFOC between metal cations and negative sea of electrons
lot of heat needed to overcome the force of attraction
why are metal malleable and ductile
cation layer can slides past each other without breaking when force is applied
layers can slides without breaking metallic bond because electrons are free to move
why are metals hard
strong EFOA between metal cation and negative sea of electrons
a lot of force needed to overcome these metallic bond
what is the structure of metallic bond
layers of positively charged metal ions in the sea of electron in a lattice
what is covalent bond
non-metal atoms form bonds with other non-metals by sharing pairs of electrons
EFOA between nuclei of atoms combining with the shared electrons
why do non metal atoms not give up electrons to gain a full outer shell?
they would have to lose too many which wld take up too much energy to overcome the pull of positive nucleus
true or false: when 2 non-metals react tgt, only one of them needs to gain enough electron to achieve a stable outer shell.
false
what is single, double and triple covalent bond and their short forms
a covalent bond when a pair of electrons is shared between 2 atoms cl-cl
a covalent bond when 2 pairs of electrons are shared between 2 atoms0=0
a covalent bonds when 3 pairs of electrons are shared between 2 atoms N≡N
what is simple molecular structure
substances with covalent bonding that made of molecules
properties of simple covalent molecules
soluble in organic solvent, insoluble in water, low m&e points, cannot conduct electricity, soft and brittle
why do simple covalent molecules have low/ high melting points
low; covalent bond between atoms in a molecule is strong but the force of attraction between the molecules ( intermolecular force) is very weak
less heat needed to overcome these weak forces between molecules
**only intermolecular force is broken not the covalent bonds between atoms
why is covalent molecules poor or good heat and electrical conductors
consist of only simple molecules and has no free moving ions/ electrons present
what are covalent compounds?
atoms of different elements share electrons
what dictates the shape of molecules?
pairs of electrons ard atoms repel each other
move as far part as they can
gives a tetrahedral shape or linear shape
why do water molecules appear to be bent
4 electrons pair ard oxygen
take up tetrahedral shape
similarities of covalent and ionic
both hv regular lattice in solid state and form crystals
2 differences between ionic and covalent in terms of forces
ionic solids particles are charged and forces are strong
molecular covalent solids particles are not charged and forces between them are weak
difference in properties of ionic and covalent compounds
ionic hv high m&b points, soluble in water and can conduct electricity when melted or dissolved in water
covalent molecules hv low m&b points, insoluble in water and do not conduct electricity
what solvent can covalent compounds dissolve in?
tetrachloromethane
what are giant covalent molecules
atoms are bonded by strong covalent bonding in a giant structure
not hold tgt by weak lattices
exist in giant covalent structure or macromolecules
what are some examples of giant covalent molecules
graphite, diamond and silicon
what are allotropes? what are allotropes of carbon
2 forms of the same element; graphite and diamond
properties of giant covalent molecules
giant covalent lattice, high m&e points, no electrical conductivity for solids, solutions or liquid, very hard
structure of diamond
each carbon atoms is covalently bonded to 4 other carbon atoms, arranged tetrahedrally in a giant structure
physical properties of diamond
hard, do not conduct electricity and high m&e points
do diamonds conduct electricity? why or why not
does not conduct; no mobile electrons as all carbon atoms have used their valence electron for bonding
why is diamond a hard material
strong covalent bonds joining atoms tgt in a tetrahedron structure
a lot of force needed to overcome the bond
why does diamond have low/ high melting and boiling points
a lot of energy needed to break the strong covalent bond that joins carbon atoms tgt in a giant structure
uses of diamond
cut edges of drills or saws because diamond is hard it good to cut edges of saw as it must cut through hard materials such as metals or ceramics
jewellery
graphite structure
each carbon atoms is bonded with 3 other carbon atoms in hexagonal carbon rings in layers
physical properties of graphite
conduct electricity, soft, high m&b points
why does graphite conduct/ not conduct electricity
conducts electricity because other shell electrons from each carbon atom is delocalised between layers
carbon atom has 4 outer electrons but only forms 3 bonds
forth electrons is free to move though graphite, carrying charge
why is graphite hard/ soft
soft
layers are attracted by weak intermolecular forces so layers easily slides over each other when force is applied
why does graphite hv high or low m&b points
high because covalent bond joining carbon atoms in layers are very strong
a lot of heat needed to overcome the bond
uses of graphite
electrical conductor (insert, conducts e, high m point)
lead
lubricant for engines and locks
structure of silicon dioxide
each silicon atoms is covalently bonded to 4 oxygen atoms and each oxygen atoms is covalently bonded to 2 silicon atoms, arranged tetrahedrally in a giant structure
physical properties of silicon dioxide and why?
hard, does not conduct electricity, high m&b points , same reasons as diamonds
