Chemical Bonding(1) Flashcards
1
Q
What is a metallic bond
A
- strong electrostatic attractions that exist between the metal ions and sea of delocalised electrons in a giant metallic structure
2
Q
Physical properties of Giant Metallic Lattice
A
- high melting points
- high electrical conductivity
— prescence of delocalised valence electrons
3
Q
Factors affecting strength of metallic bond
A
- no. of valence electrons electrons available for metallic bonding
- ionic radius of metal cation
4
Q
What is Ionic bond
A
- strong electrostatic attractions that exist between the cation and anion in the ionic lattice
5
Q
What are physical properties of ionic bonding
A
- high melting point
- soluble in water and other polar solvents
- good electrical conductor when in molten state or aqueous
- non-electrical conductor in solid as ions can only vibrate about fixed positions
6
Q
Factors affecting strength of ionic bond
A
- charge and size of ionic radius
- larger the charge size and smaller the ions the stronger the electrostatic forces of attraction
- charge density is irrelevant
7
Q
What is a coordination number
A
- no. of nearest ions that surround another ion of the opposite charge in an ionic lattice
- relative size of ions and charge
8
Q
What is a covalent bond
A
- strong electrostatic attraction between a shared pair of electrons and two positively charged nuclei
9
Q
What is a sigma bond
A
- valence orbitals overlap along inter-nuclear axis, a single region of head-on overlap is produced
10
Q
What is a pi bond
A
- side-on overlap of p orbitals will result in two regions of overlap
11
Q
What is a co-ordinate bond(dative bond)
A
- shared electron pair comes from one atom
- donor has lone pair of electrons, acceptor has vacant low lying orbitals
12
Q
What is electronegativity
A
- measure of its ability to attract the shared pair of electrons in a covalent bond to itself
- increases across period
- decrease down the group
13
Q
What is bond polarity
A
- difference in electronegativity
- bonding electrons are drawn towards more electronegative atom
- more electronegative atoms will acquire partial negative while the other a partial positive charge
- permanent separation of charges is a dipole
14
Q
Strength of covalent bond
A
- bond energy and bond length are indicators of strength of covalent bond
15
Q
Bond energy
A
- amount of energy required to break one mole of covalent bond between 2 atoms in gaseous state
- stronger the covalent bond —> higher bond energy
16
Q
Bond length
A
- distance between nuclei of two atoms in the bond
- shorter bond length indicates stronger covalent bond
17
Q
Factors affecting covalent bond strength
A
- effectiveness of orbital overlap
- difference in electronegativity between bonding atoms
- number of bonding electrons
18
Q
How does effectiveness of orbital overlap affect covalent bond strength(from Cl to I)
A
- As atoms from Cl to I becomes larger, size of valence orbitals increases
- these larger orbitals become more diffused and when they overlap, the accumulation of electron density with inter-nuclei region is lower
- orbital overlap is less effective resulting in weaker bond strength
19
Q
How does difference in electronegativity between bonding atoms affect covalent bond strength
A
- since electronegativity increases in the order N<O<F, bond polarity increases in the order N-H<O-H<F-N
- in addition to existing covalent bond there is increase in the electrostatic attraction between the two partial charges
- therefore an increase in bond strength
20
Q
How does number of bonding electrons affect strength of covalent bond strength
A
- as number of bonding electrons increases within the inter-nuclei region for multiple bonds,
- the attractive forces for these electrons increases
- covalent bond strength increases
