Answer:
They conducted it from earth
Explanation:
There had never been anything capable of observing it from space launched at that time because Sputnik wasn't even launched
Answer:An atom consists of three sub atomic particles which are protons, neutrons, and electrons. Protons have a positive charge, neutrons have no charge, and electrons have a negative charge.
Explanation: because atoms are made up of particles
Answer:
In a volumetric flask of marking 500.0 mL add 138.75 grams of calcium chloride and add small amount of water to dissolve solute completely. After the solute gets completely soluble add more water up till the mark of 500 ml.
Explanation:
Concentration of calcium chloride = 2.5 M
Volume of the solution = 500.0 ml = 0.5000 L
Moles of calcium chloride = n

n = moles of solute
c = concentration of solution
V = volume of the solution in L




Mass of calcium chloride = 111 g/mol × 1.2500 mol = 138.75 g
In a volumetric flask of marking 500.0 mL add 138.75 grams of calcium chloride and add small amount of water to dissolve solute completely. After the the solute gets completely soluble add more water up till the mark of 500 ml.
Answer:
AlN has highest melting point among given.
Explanation:
As per ionic model, ionic compounds are held together by electrostatic force. The ionic compound having strong electrostatic force will have high melting point.
Electrostatic force is proportional to charge and size of constituent ions.

In case of MgO
Charge on Mg = +2
Charge on O = -2

In case of LiF
Charge on Li = +1
Charge on F = -1

In case of AlN
Charge on Al = +3
Charge on N = -3

In case of RbF
Charge on Rb = +1
Charge on F = -1

In case of CaS
Charge on Ca = +2
Charge on S = -2

As magnitude of electrostatic force is highest in AlN, therefor, it has highest melting point.