Which of the following compounds is not likely to have ionic bonds lif, naci, ch4, mgf2

Methane CH does not have ionic bonds. Because of the close value of electronegativity of the carbon and hydrogen atoms the electrons are shared forming covalent bonds.

 is not likely to have ionic bonds

Explanation:

Ionic bond is formed between a metal and a non metal.

and are examples in which we see metal bonded with a non-metal.

Na, Li, Mg are all metals and Cl, F are non metals.

contains only non metals. Covalent bond is the bond present among non metallic compounds.

We can identify a bond as an ionic bond or a covalent bond based on the electronegativity values of the atoms present in it.

For example

Hydrogen --> electronegativity value is 2.1

Sulfur --> electronegativity value is 2.5

∆E, the electronegativity difference is 2.5 - 2.1 = 0.4

So, It is a non polar covalent bond present in

Examples :  

The electronegative values of H is 2.1

F is 4.0

O is 3.5  

N is 3.0

∆E value of HF Hydrogen bond  is

4.0 - 2.1 = 1.9

∆E value of H2O Hydrogen bond is

3.5 - 2.1 = 1.4

∆E value of NH3 Hydrogen bond is

3.0 - 2.1 = 0.9

∆E value between 0.5 to 1.7 is a polar covalent bond

∆E value btween 0 to 0.4 is a non polar covalent bond  

∆E above 1.7 is an ionic bond

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.