Four elements arbitrarily labelled a, b, c, and d have electronegativities of 3.8, 3.3, 2.8, and 1.3, respectively. place the compounds ab, ad, bd, and ac in order of increasing covalent character

AD < BD < AC< AB

Explanation:-

Electronegativity is defined as the property of an element to attract a shared pair of electron towards itself.

Lower is the electronegativity diffrence, more will be the covalent character. Higher is the electronegativity diffrence, more will be the ionic character.

1. AB:  Electronegativity difference = electronegativity of A - electronegativity of B = 3.8-3.3= 0.5

2. AD: Electronegativity difference = electronegativity of A - electronegativity of D= 3.8-1.3=  2.5

3. BD: Electronegativity difference = electronegativity of B - electronegativity of D= 3.3-1.3= 2.0

4. AC: Electronegativity difference = electronegativity of A - electronegativity of C= 3.8-2.8= 1.0

Thus the order of increasing covalent character is AD < BD < AC< AB.