📚🔥Chemistry 1.4 -bonding Flashcards by jessica gregory

Define an Ionic Bond

A bond formed by the electrostatic attraction between positive and negative ions (actions and anions)

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Define a Covalent bond

Has a pair of electrons with opposed spin shared between two atoms with each atom giving one electron

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Define a co-ordinate bond

A covalent bond in which both electrons come from one of the atoms

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Give an example of a covalent bond

A bond between two non metals e.g CL2

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Give an example of an ionic bond

A bond between a metal and non metal for example Na + Cl —> NaCl

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What happens to the electrons shared in a covalent bond?

the electrons repel each other but this is overcome by their attraction to both nuclei

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What must be so that covalent bonds form?

The electrons spins must be opposite for the bonds to form

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How are ions arranged in ionic bonding to minimise repulsion

In ionic bonding cations and anions are arranged so that each cation is surrounded by anions and vica Verda to maximise attraction and minimise repulsion

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Describe a metallic bond

A lattice of positive ions held together by a ‘sea’ of delocalised electrons given up by each atom

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Describe the electro negativity in a covalent bond

The electron pair is not shared evenly between atoms, one will have a slightly greater electronegativity than the other forming a slightly polar bond

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Why are co-ordinate bonds always polar?

Because the atom giving both electrons can’t loose both its rights

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Define intermolecular bonding?

The bonding between molecule

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Define an intramolecular bond

Bonding within molecules

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Name 2 properties of intermolecular bonding:

Low melting/boiling point

- bonding within molecules is strong and generally govern chemical reactivity

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What causes intermolecular bonding

It is caused by electrical attraction between opposite charges

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Explain how neutral molecule may be a dipole (e.g H20)

Because it contains bonds that may have a difference in electronegativity and therefore the molecule will be dipole

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Name a example of a molecules with non dipole show intermolecular bonding

Helium atoms come together to form a liquid at 4K

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Explain why molecules with no overall charge experience intermolecular bonding

Because the electrons are in constant motion around the nuclei so the centre of ‘+’ and ‘-‘ charge don’t balance producing a fluctuating dipole

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Explain how one He molecule would bond to another via intermolecular bonding

The fluctuating dipole induces am opposite dipole in a nearby molecule creating attraction

Explain van der Waals forces

Electrons in atoms are moving around at any point so they are unlikely to spread evenly
This gives a molecule a temporary dipole
The dipole moment indices a temporary dipole in a neighbouring molecule/atom by attracting its electron charge cloud
These small induced dipole attract one another creating weak intermolecular forces know as van der Waals forces

What kind of bonding is present in hydrogen bonding?

What elements is hydrogen bonding most likely to occur with?

Strong dipole-dipole interaction between H atom, one a very electronegative element having lone pairs namely fluorine, oxygen and nitrogen

Which bonding is stronger hydrogen bonding or van der Waals?

Hydrogen bonding is much stronger than van der Waals forces

What structure does ice have?

An open lattice with hydrogen bonds holding water molecules apart

What happens to the bonding when ice melts?

When ice melts the rigid hydrogen bonds collapse allowing the water molecules to move closer together

What is the effect of increased temperature on van der Waals forces?

As the strength of the intermolecular force increases boiling and melting point of a temperature also increases

What happened to the boiling point of a van der Waals force as molecular mass and dipole increases

As the molecular mass / dipole increases the boiling point also increases

Explain why water has an unusually high boiling point compared to the rest of group 6

Water has free hydrogen bonds which are very strong intermolecular forces, this means that a greater value of KE is needed to break such bonds increasing its boiling temperature to 100 degrees

Why are polar molecules soluble?

Because they have a difference in electronegativity meaning the molecules can attract water molecules forming hydrogen bonds

Why are non polar molecules insolvable?

No difference in electronegativity and therefore no overall charge meaning the molecule does not interact with the water molecule

What bond is present if there is a large difference in electronegativity?

Ionic bonding

What bond is present if there is a small difference in electronegativity?

Polar covalent bond

Summarise the main features of an ionic bond:

- complete transfer of electrons | - metal + non metal

Summarise the main features of a pure covalent bond:

- equal sharing of electrons - no charge - 2 identical non metals e.g H-H bond

Name the two stages that fall between pure ionic and pure covalent bonding

- polar ionic (unequal sharing or electrons, partial ionic charges, 2 different non metals) - polar covalent

What does VSEPE theory stand for?

Valence Shell Electron Pair Repulsion

Define VSEPR theory

“Bonding and lone pros know the outer shell of an atom will repel each other and take up position as far apart as possible”

Why do lone pairs and bonding pairs repel each other?

Lone pairs of electrons are closer to the centre of the atom then bonding pairs, since they occupy a smaller volume the charge density is higher meaning that the lone pairs repel more strongly than the bonding pairs reducing the bond angle

Name the shape which features at 90 degrees, it’s value of electron clouds and lone pairs

Octahedral, 6 electron clouds and 0 lone Pairs

Name the shape which features at 105 degrees, it’s value of electron clouds and lone pairs

Non linear, 4 electron clouds and 2 lone pairs

Name the shape which features at 107 degrees, it’s value of electron clouds and lone pairs

Pyramidal, 4 electron clouds and 1 lone pair

Name the shape which features at 109.5 degrees, it’s value of electron clouds and lone pairs

Tetrahedral, 4 electron clouds and 0 lone pairs

Name the shape which features at 120 degrees, it’s value of electron clouds and lone pairs

Trigonal Planer, 3 electron clouds and 0 lone pairs

Name the shape which features at 180 degrees, it’s value of electron clouds and lone pairs

Linear, 2 electron clouds and 0 lone pairs

Name the VSEPR repulsion sequence

Lone pair-lone pair > lone pair-bond pair > bonded pair- bonded pair

What happens to the bond angle if there are no lone pairs

The bonding pairs will repel each other equally compressing the angle

What happens if there are lone pairs and bonding pairs

The lone pairs will repel the bonding pairs strongly which compresses the bond angle