Answer:
C) 1 and 3
Explanation:
A period in the periodic table is a row of chemical elements. All elements in a row have the same number of electron shells. ... Arranged this way, groups of elements in the same column have similar chemical and physical properties, reflecting the periodic law.
Answer:
salt will dislove sand wont
Explanation:
Rubidium is a alkali metal.
Bohr changed the model of the atom by proposing that electrons travelled in circular orbits with specific energy levels.
Answer: The structure for the boron nitride molecule will be linear.
Explanation: When boron and nitrogen combine together to form a compound, the boron element will loose 3 electrons which will be easily accepted by the nitrogen element.
Boron : Atomic number is 5
Electronic configuration: 
To attain stable configuration, boron will loose 3 electrons easily.
Nitrogen : Atomic number is 7
Electronic configuration: 
To attain stable configuration. nitrogen will gain 3 electrons easily.
Hence, to form a molecule with these two elements, there will be 3 bonds present in between them and 1 pair of lone pair will be left on the nitrogen atom.
Structure of boron nitride ( which is linear) is attached in the image below.