Atomic Structures Part 2 Flashcards
what is an ionic bond. How does it work?
an actual transfer of electrons from the metal and the non-metal. The transfer creates two opposite charges that are attracted to eachother holding them together
what are the two components of an ionic bond
an element with low ionization energy (metal) and an element with a high ionization energy (non metal)
describe an ionic solid at room temperature
they are solid because of the attraction between the ions is very strong
how are atoms arranged in an ionic solid?
in a highly ordered crystal lattice structure, maximizing attractive forces and minimizes repulsive forces
how do ionic compounds behave in water
are slightly soluble and will conduct electricity as ions are free to move to oppositely charged electrodes
what is a covalent bond
when electrons are shared between nucleuses to achieve a full outer energy level
what type of atoms are present in a covalent bond?
2 atoms with high ionization energies
in a covalent bond when are electrons shared equally?
when the electronegativity different between the atoms is less than 0.4
in a covalent bond when is it a polar bond?
the electronegativity difference between the two atoms is between 0.4 and 1.7 which leads to an unequal sharing of electrons
when will a MOLECULE be polar?
if it is assymmetrical and contains polar covalent bonds
what is a coordinate covalent bond
when both electrons being shared come from the same atom
describe non-polar covalent solids by themself
have low melting and boiling points and are often gases at room temperature due to the low intermolecular forces that exist in these molecules (LDF only)
if they are solid at room temperature usually soft and waxy
describe non-polar covalent solids in water
soluble in non-polar solvents like etheres, but won’t conduct electricity as they lack charged components
what are some properties of polar covalent molecules
tend to have higher melting and boiling points and are more likely to be liquids or solids at room temp
describe polar covalent molecules in water
will dissolve in polar solvents and will not conudct electrivity as very few particles to ionize
what is a metallic bond?
when both atoms have low ionization energies and low electronegativities and will lose electrons easily - like 2 metals
describe the electrons in a metallic bond
positive metal ions are arranged with valence electrons delocalized around them, thus they are mobile and move throughout the metal structure
what are the properties of metallic compounds
- malleable and ductile
- good conudctors of heat and electricity
- shiny
- solid at room temp
- have a photoelectric effect
why are metallic ompounds malleable and ductile?
atoms are restrictied to one position by a fixed bond and the ions can roll past each other
why are metallic compounds good conductors of heat and electricity
because electrons are mobile and can’t transmit energy rapidly
why are metallic compounds shiny?
because when light strikes a metal the valence electrons absorb energy and oscillate at the same frequency as the incidient light and then emit light as a reflection of the original light
why are metallic compounds solid at room temperature?
due to the strong bonds
what is the photoelectric effect?
electron emission caused by heat or light occurs when the frequency of light strikin a metal is sufficient to overcome to attractive forces and an electron escapes the metal decreasing the energy of the photon
what is a network solid?
a macromolecule - a gient structure of covalently bonded atoms in one, two or three dimensional arrays
what are allotropes?
elements that exist in different physical forms with different physical properties but the same chemical properties
what is a 3-dimensional network solid?
network solid consists of covalently bonded atoms which form regular 3-D arrays or crystals
what are some properties of 3-dimensional network solids
- very strong bonds s
- high melting and boiling points
- solid and room temperature, be extremely hard
- not soluble in any solvent
- do not conduct electricity
what are some examples of 3-dimensional network solids?
diamond, quartz, and silicon carbide
what is a 2-dimensional network solids
network of covalent bonds that form 2-D arrays or sheets
the layers are held together by van del Waals forces
describe the properties of 2-dimensional network solids
- high melting and boiling points
- soft and the layers will slides over each other allowing them to be used as a lubraicant
what is an example of 2-dimensional network solids
graphite
what is a 1-dimensional network solids
solids that form networks of a one dimension array or fibre - a long chain held together by covalent bonds - between adjacent chains attractive forces are very weak
describe the properties of 1-dimensional network solids
- very high melting and boiling points due to strong covalent bonds
- solid and room temp
- NOT soluble in water
what is an example of a 1-dimensional network solid
asbestos
describe quartz
- 3-dimensional network
- each silicon tetrahedrally bonded to four oxygen atoms
- foreign metal ions in quartz produce semiprecious stone like emerald, amethyst and garnet
describe mica
- 2-dimensional sheets of silicate Si + O
- mica flakes
who came up with the valence bond model?
Linus Pauling
What does the valence bond model say?
it exists to explain how atoms come together to form molecules
covalent bonds form when two orbitals overlap to produce a new combined orbital containing two electrons of opposite spin which results in a decrease in the energy of the atoms forming the bond, most likely to found between the two nuclei forming the bonds
what must be true for atoms to bond according to the valence bond model?
the orbitals combining must start with an unpaired electron
what was wrong with the valence bond theory?
cannot be used to explain the bonding in most covalent compounds and polyatomic ions and cannot be used to explain multiple bonds
what points from the valence bond theory remained valid?
- simple molecules can bond according to the valence bond theory with regular orbitals
- a covalent bond results from the overlapping of 1 orbital from each atom in the bond.
what does hybridization theory hypothesize?
the central atom makes new orbitals before bonding with the other atom, which are called hybrid orbitals
how are hybrid orbitals formed?
by combining the atom’s atomic s, p and d orbitals
what must be true for hybrid orbitals to be created?
the orbitals being combined must all come from the same energy level
and for each hybrid orbital needed you must use 1 atomi orbital
a set of hybrid orbitals all have equal energy
when are hybrid orbitals needed?
- sigma bonds
- lone pairs
- co-ordinate covalent bonds
what is a sigma bond?
1 hybrid orbital with a electron
what is a lone pair
1 hybrid orbital with 2 electrons
describe a co-ordinate covalent bon in relation to hybrid orbitals
1 hybrid orbital with 2 electrons or an empty hybrid orbital
what is a pi bond?
additional bond to make double/triple bonds
describe a pi bond
do not hybrid orbitals - formed using regular atomic p orbitals with 1 electron
what is a bonding orbital
lower energy and greater stability this is where there is a greater possibility to find the electrons between the nuclei of the atom
what is an antibonding orbital
higher energy and lower stability, low possibility to find the electrons between the nuclei of the atom
