Question

1. Sketch the shape of the periodic table and describe (don't need to include elements) and explain the significance of the rows and columns in terms of:

Number of electron shells

Number of electrons in the outer shell

How covalent, ionic and metallic bonds form

2. Sketch the four different bond types discussed in class, state the relative strength of each and provide one example (a mineral) of each.

please be very detailed, thank you

Answer 1

Significance of colums : The vertical columns are known as groups or families. the present periodic table consists of 18 vertical columns. each group consist of a number of elements having same electronic configuration of the outermost shell. these groups are numbered from 1 to 18. the total number of outermost electrons(valence electrons) is same in a particular group. (as given by general electronic configuration)

Significance of rows : there are seven horizontal rows known as periods . these are numbered as 1 to 7. the period number corresponds to highest principal quantum number (n) of the elements in the periodic table. The principal quantum number gives the number of shells and subshells present in an element.

Also, 14 elements of sixth period called the LANTHANOIDS and 14 elements of seventh period called the ACTINOIDS are placed in separate panel at the bottom.

Trends in mettalic and non metallic character : the metallic character increases from top to bottom within a group and non metallic character increases from left to right along a period. this change from metallic to non metallic character is not abrupt as shown by zig zag line (red line) in the table.. the elements silicon, germanium , arsenic , antimony and tellurium shows the properties of both metals and non metals. these are called metalloids.

types of chemical bond :

1) Ionic bond : when a bond is formed by complete transfer of electrons from one atom to another so as to complete their octet by acquiring 8 electrons (or duplet i.e 2 electrons in case of hydrogen and helium ) and hence acquire noble gas configuration , the  bond is called ionic or electrovalent bond.

example : NaCl , CaF2

formation of ionic bond involves

• formation of positive ion by loss of elctrons from one kond of atoms
• formation of negative ion by gain of ekctrons from one kind of atoms
• electrostatic force of attraction holding positive and negative ions together.

2) covalent polar bonds : the bond formed between two atoms by mutual sharing of electrons between them so as to complete their octets and duplets is called covalent bond. if the two atoms have different electronegativities then the shared paired of elctrons will be attracted more towards the more elctronegative atom and thus the bond formed is polar .

for example : H-Cl , H2O , CO

the number of electrons contributed by each atom is known as covalency.

3) non polar covalent bonds : the covalent bond between two same atoms (thus same electronegativity) is non polar as the shared paired of elctron is equally shared between the two.

for example : -C=C- , H-H, O=O

4) Metallic bonds : metallic bond can be defined as the forces of attraction between electrons and positively charged metal cations. these free or detached electrons are called kernels. metallic compounds are good conductor of electricity.

5) dative bonds : during the formation of bond , if both the electrons are donated by one atom but shared by both the atoms so as to complete their octets, the bond formed is called dative bond.

for example : bond between NH3 and BF3

Relative strength of bonds :

dative and covalent bonds are of equal strength.

The strength of covalent bonds is determined in terms of bond dissociation energy . greaterthe B.D.E , greater will be the bond strength.

The strength of ionic bonds is determined in terms of lattice energy.

covalent bonds are stronger than ionic bonds because they involve sharing of electrons (which in turn involve overlapping of orbitals) while in ionic bonds only electrostatic force of attraction between oppositively charged ions is there.

ionic bonds are stronger than metallic bonds .