CHEM1011 Lecture Notes - Lecture 7: Electron Configuration, Noble Gas, Covalent Bond

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24 May 2018

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Lecture 7: Covalent bonding

Ionic bonding

- It takes energy to remove an electron from an atom

- Electrostatic attraction between cations and anions supplies energy

- Generally, do not get very highly charged ions as too much energy is required to form

them

Sharing of electrons

- In ionic compounds, a noble gas electron configuration is obtained by transfer of

electrons

- In covalent compounds, a noble gas electron configuration is obtained by sharing of

electrons

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Hydrogen

Reasons for covalent bonding

- Electrons are shared to achieve a noble gas configuration for each atom

- Electron density between two atoms: the bond is directional (electrons are not like

Bohr’s odels- they are more like clouds)

 when atoms share electrons, it is dense

 need to get electron density

 the angle at which an electron comes in is important, it cannot just join an atom

wherever

- only electrons from the outermost shell can be involved in bonding – valence electrons

- electrons tend to form pairs (e.g. 4 pairs in the second shell)

 a’t ake a od etwee 3 atos (1 electron from each)

Valence

- valence electrons are used in bonding

- the valence of an atom is the side of the charge if it forms an ion or the number of

bonds it forms in a neutral molecule

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Document Summary

It takes energy to remove an electron from an atom. Electrostatic attraction between cations and anions supplies energy. Generally, do not get very highly charged ions as too much energy is required to form them. In ionic compounds, a noble gas electron configuration is obtained by transfer of electrons. In covalent compounds, a noble gas electron configuration is obtained by sharing of electrons. Electrons are shared to achieve a noble gas configuration for each atom. Electron density between two atoms: the bond is directional (electrons are not like. When atoms share electrons, it is dense. The angle at which an electron comes in is important, it cannot just join an atom wherever. Only electrons from the outermost shell can be involved in bonding valence electrons. Electrons tend to form pairs (e. g. 4 pairs in the second shell) (cid:272)a(cid:374)"t (cid:373)ake a (cid:271)o(cid:374)d (cid:271)etwee(cid:374) 3 ato(cid:373)s (1 electron from each)

Related Questions

1. True or False. a. A positively charged ion is called an anion. b. If an atom gives up an electron, it creates negatively charged ion. c. Valence electrons are the electrons that are available for bonding and located in the shells closest to the nucleus. d. An ionic bond is the result of electron sharing. e. When atoms gain, lose, or share electrons they do so in order to have an electron configuration of a noble gas. f. As you go across the periodic table left to right, electronegativity will increase. g. The number of valence electrons an atom has is equal to the atomic number. h. Fluorine cannot be the central atom due to the fact that is can only accept 2 electrons. i. When a covalent bond occurs, the atoms overlap one another to create a new orbital. The more overlapping, the stronger the bond. j. A triple bond is considered to be a weak bond.

Answer to the following short questions:

1. What is the percentage of chlorine present in ?

2. What is the volume in of of oil if its density is ?

3. Find the error(s) and rewrite the text in the correct form.

“According to the Dalton model for the atomic structure, the atomic structure is composed of a nucleus in the center and electrons orbiting around it. The Nucleus has always the same number of protons and neutrons and they are located in the Nucleus. The nucleus carries almost the whole of the mass of the atom. The nucleus is positively charged and the electron is negatively charged. Anions are obtained when electrons are lost. Anions and Cations form salts via ionic bonding. Salts are always soluble in water. All Covalent compounds (molecules) are not soluble in water”.

4. What is the oxidation number of the Sulphur atom in ?

5. The following equation describes the burning of hexane in oxygen: How many moles of water would be produced if of hexane was burnt in excess oxygen?