2.5 electrons and bonding

what is meaning of electron shell?

a group of atomic orbitals with the same principle quantum number, n. Also known as a main energy levels

what is meaning of sub-shells?

a group of orbitals of the same type within a shell

what is meaning of orbitals?

a region within an atom that can hold up to two electrons with opposite spin

describe the shape of s-orbitals?

spherical shaped

describe the shape of p-orbitals?

dumbbell shaped

what are two elements have a weird rule to electronic configuration?

• chromium (Cr)

• copper (Cu)

how is Cr and Cu act different for electronic configuration?

• they want a full d orbital so they take from the s orbitals

what is another word for the shell number or energy level number?

quantum number

what is the formula to know how many electrons in a shell?

2n²

what are the three separate p-orbitals?

px

py

pz

what are the differences between the three p-orbitals?

the angles

4s and 3d energy levels are overlapping but which one has more energy?

3d has higher energy level

4s and 3d energy levels are overlapping but which one gets filled first?

4s gets filled first

why do orbitals have opposite spin?

to help counteract the repulsion between the negative charges of two electrons

what are blocks?

the periodic table can be split into blocks according to their highest energy sub-shell

what is the s-block?

highest energy electrons in the s-sub-shell

(left block of the 2 groups)

what is the p-block?

highest energy electrons in the p-sub-shell

(right block of 6 groups)

what is the d-block?

highest energy electrons in the d-sub-shell

(centre block of 10 groups)

what is ionic bonding?

electrostatic attraction between positive and negative ions

how would you draw ionic bonding?

dot and cross diagrams

what are physical properties of ionic compounds?

• giant ionic lattice structure

• ionic bonding

do ionic compounds have a high/low boiling point and melting point?

high

what ionic lattices have a higher boiling point? And why?

Ions with greater charges because there is a stronger attraction between ions.

And the sizes of the ions

what do many ionic compounds dissolve in? And why?

polar solvents like water because polar water molecules break down the lattice and surround each ion in the solution

when will an ionic compound not be very soluble?

when ions have large charges, the ionic attraction may be too strong for water to break down the lattice structure

what are the two processes which is required for solubility?

• ionic lattices must be broken down

• water molecules must attract and surround the ion

when does ionic compound conduct electricity?

molten or dissolved in water

why do solid ionic compounds not conduct electricity?

ions are fixed in position in the giant ionic lattice and so there are no mobile charge carriers

why do liquid or dissolved in water compounds conduct electricity?

solid ionic lattice breaks down so ions are now free to move as mobile charge carriers

what is covalent bonding?

strong electrostatic forces of attraction between a shared pair of electrons and the nuclei of the bonded atom

what does it mean if a covalent bond is localised?

attraction is solely between the shared electrons and the nuclei of the two bonded atoms

what is a molecule?

smallest part of a covalent compound that can exist whilst retaining the chemical properties of the compound

how would you draw covalent bonds?

• dot and cross diagram

• displayed formula

what are lone pairs?

paired electrons which are not shared

what is a dative covalent or coordinate bond?

covalent bond in which the shared pair or electrons have been supplied by one of the bonding atoms only

what is the average bond enthalpy?

measurement of covalent bond strength. The larger the value, the stronger the covalent.

what does a single bond count as?

1 bonding pair

what does a double or triple bond count as?

1 region of electron density which counts as the same as bonding pair

do bonding pairs repel or attract each other?

repel

what do lone pairs count as? And do they repel more or less than bonding pairs? What does this do?

a region of electron density

repel more than bonding pairs, decreasing the bond angle around the central atom