Chemistry Answers

Answer # 1:
Ionic Bonds:
A molecule or an atom that losses or gains electrons are called ions. Atoms from cations, when they lose electrons or anions when they gain electrons. Ionic bond is basically a strong bond formed when oppositely charged ions are attracting to each other. Ionic bonds are non-directional bonds might be attracted to one another in any direction. For example:
Sodium atomic radius = 0.192 nm Chlorine atomic radius = 0.099 nm
Sodium ionic radius = 0.095 nm Chlorine ionic radius = 0.181 nm
Covalent Bonds:
Covalent bonding consists of sharing one or more electrons pairs between atoms. Elements that tend to form covalent bonds are those that are:
1. Having similar electronegativity’s.
2. Not strongly electropositive
3. Strongly electronegative
Covalent bonds can be formed not

It gives metals their unique properties that we don't see in non-metal substances. Metallic bonds are:
1. Directionless bonds
2. High symmetry and density bonds

Answer # 2:
The study of the crystal structure of metals is important due to following reasons:
1. The properties of few materials are directly related to their crystal structure, for example pure and undeformed beryllium and magnesium, having one crystal structure are much more brittle than are pure and undeformed metals such as silver and gold that have yet another crystal structure.
2. Knowledge of crystal structure of iron helps us to understand transformations that occur when steels are heat treated to improve their mechanical properties.
3. Moreover, significant property differences exist between non- crystalline and crystalline materials having the same composition.
Answer # 3:
In Face Centered Crystal structure number of atoms per unit cell is equal to four. In FCC unit cell we have:
6 face atoms shared by two cells = 6/2 = 3
8 Corner atoms shared by 8 cells = 8/8=