Explanation:
Ionic crystals
1. They are formed by electrostatic attraction between the cation and anion.
2. Naturally solid and brittle in nature.
3.Generally good conductors of electricity in moltane state and have high melting and boiling points.
Example: NH4Cl is an inonic compound with NH4^+ being cation and Cl- being anion.
Molecular Solid
1. These are formed by sharing of electrons pair between the atoms. A shared pair of e- is called a covalent bond.
2. Usually not a good conductor of electricity even in melted state.
3. They mostly liquids and gases only a few are solids.
examples , CO, CO2 , H2CO3 , etc.
Answer:
3.2 Calories
Explanation:
Here we will use a formula
Heat added in calories = Mass of glass x Increase in temperature x specific heat of glass
As we know that, specific heat is the amount of energy required to raise the temperature of one gram of any substance by 1°C. It has a constant value for every substance and for glass the specific heat is .16 calories/gm
Incorporating the values of mass (m), temperature(T) and specific heat (c) in formula.
calories (small calories) = l.0 g x 20 degrees x .16 calories/gm/°C
= 3.2 calories
Hope it helps:)
To Find :
How many moles are in 
atoms of iron.
Given :
We know, 1 mole of any element or compound contains exactly 
( Avogadro's Number ) atoms/compound .
Now, 
So, number of moles in given number of atoms are :
Hence, this is the required solution.
