Chapter 5 - Electrons and Bonding Flashcards
how many electrons fill shell number 1?
2
how many electrons fill shell number 2?
8
how many electrons fill shell number 3?
18
how many electrons fill shell number 4?
32
what are shells?
- shells are regarded as energy levels
- the energy increases as the shell number increses
- the shell number/energy level number is called the principal quantum number
what is an atomic orbital?
a reigon around the nucleus where there is a high probability of finding an electron
what are the properties of orbitals?
- an orbital can hold one or two electrons but no more
- there are different types of orbitals
- each type of orbital has a different shape
what are the different types of orbitals?
s-, p-, d- and f- orbitals
what are the properties of s- orbitals?
- sphere shaped
- each shell from n=1 contains 1 s-orbital
- radius increases with shell number
what are the properties of p- orbitals?
- dumb-bell shaped
- there are 3 at right angles to eachother
- each shell from n=2 contains 3 p- orbitals
- distance from nucleus increases with shell number
what are the properties of d- and f- orbitals?
- each shell from n=3 contains 5 d- orbitals
- each shell from n=4 contains 7 f- orbitals
what sub-shells are present in shell 1?
1s
what sub-shells are present in shell 2?
2s and 2p
what sub-shells are present in shell 3?
3s, 3p and 3d
what sub-shells are present in shell 4?
4s, 4p, 4d and 4f
in which order do orbitals fill?
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 4d, 4f
how are electrons drawn in the electrons-in-box model?
as two arrows, one up and one down as they have opposite spins
why do electrons have opposite spins?
the opposite spins help counteract the repulsion between the negative charges of the electrons
how would 4 electrons occupy the p-orbitals?
2 in the first sub shell, 1 in the second sub shell and 1 in the last sub shell as electrons repel each other
how do you express electron configuration in short hand?
previous noble gas + outer electron sub shells
when are cations formed?
when atoms lose electrons (positive ions)
when are anions formed?
when atoms gain electrons (negative ions)
which shell empties first when electrons are lost: 4s or 3d?
4s empties before 3d
(first in, first out)
what is a dot-and-cross diagram in ionic bonding??
- electrons are shown as dots or crosses
- outer shell electrons from one atom are transferred to another
- positive and negative ions are formed with a full outer shell
what is the stucture of an ionic compound and why?
ions attract oppositely charged ions in all directions, so a giant ionic lattice of positive and negative ions where each ion is surrounded by oppositely charged ions is formed
what is the trend in melting and boiling points of ionic compounds?
- almost all are solid at room temp as there is insufficient energy to overcome the strong electrostatic forces of attraction between the oppositely charged ions
- high temperatures are needed to overcome the attraction so melting and boiling points are high
what is the trend in solubility of ionic compounds?
- ionic compounds dissolve in polar solvents (e.g water)
- polar molecules break down the lattice and surround each ion in solution
- in a compound with ions of large charges ionic attraction may be too strong for water to break down the lattice structure so the compound wont be very soluble
what is the trend in electrical conductivity of ionic compounds?
- when solid ions are in a fixed position in the lattice and there are no mobile charge carriers so the compound will not conduct electricity
- when liquid or dissolved the lattice breaks down so ions can move as mobile charge carriers so the compound will conduct electricity
what is ionic bonding?
the electrostatic attraction between positive and negative ions in an ionic compound
what is covalent bonding?
the strong electrostatic attractions between a shared pair of electrons and the nuclei of the bonded atoms
what does covalent bonding occur between?
non-metallic elements, compounds of non-metallic elements and polyatomic ions
what does ionic bonding occur between?
cations and anions
what is a covalent bond?
the overlap of atomic orbitals where
- the shared pair of electrons is attracted to both nuclei
- the bonded atoms often have outer shells with the same electron structure as the nearest noble gas
what is the stucture of a covalent compound and why?
the attraction is localised, acting solely between the shared pair of electrons and the nuclei of the two bonded atoms. this means a small unit called a molecule (the smallest part of a covalent compound) is formed
what is the displayed formula of a covalent compound?
- a displayed formula shows the relative positioning of atoms and the bonds between them as lines
- lone pairs are added as dots
how many covalent bonds does carbon form?
4
how many covalent bonds does nitrogen form?
3
how many covalent bonds does oxygen form?
2
how many covalent bonds does hydrogen form?
1
how many covalent bonds does boron form?
boron forms covalent compounds in which its 3 outer shell electrons are paired, so sometimes only has six electrons around the boron atom
what is expansion of the octet?
covalent compounds with more than 8 electrons in the outer shell
when is expansion of the octet possible?
from the n=3 shell, when more than 8 electrons can be held in the outer shell
what is a double bond?
when the electrostatic attraction is between two shared pairs of electrons and the nuclei of the bonded atoms (e.g O2 and CO2)
what is a triple bond?
when the electrostatic attraction is between three shared pairs of electrons and the nuclei of the bonded atoms (e.g N2)
what is a dative covalent bond?
a covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only. the shared pair was originally a lone pair of electrons on one of the bonded atoms
what is average bond enthalpy?
a measurement of covalent bond strength
