Answer:
Explanation:
A physical change is a change in which the physical properties of matter are altered. These are properties are the forms and state.
Most physical changes are easily reversible and are pure state changes.
They do not lead to the production of new compounds.
They involve no mass change and requires little to no energy.
Examples are melting, boiling, freezing, sublimation e.t.c
Answer:
25.30 gram
Explanation:
No of moles = given mass / molar mass
No of moles = 63.17/80.06
0.7890 moles
Mass of sulphar = no of moles× molar mass of sulphar
Mass of sulphur = 0.7890×32.065
25.30 gram
The correct answer is:
A positively charged nucleus is surrounded by one or more negatively charged electrons
The explanation:
when:
proton is a positively charged elementary particle that is a fundamental constituent of all atomic nuclei.
neutron is a subatomic particle found in the nucleus of every atom except that of simple hydrogen. The particle derives its name from the fact that it has no electrical charge
electron is a negatively charged subatomic particle. It can be either free (not attached to any atom), or bound to the nucleus of an atom .
so, , there are positively charged protons and zero-charged neutrons in the nucleus of an atom. Therefore, the nucleus is positively charged, Surrounding the nucleus, the electrons have negative charge.
Thus, the correct answer is (3): A positively charged nucleus is surrounded by one or more negatively charged electrons is correct.
Answer:
second energy level
Explanation:
Valence electrons are those electrons which are present in outer most orbital of the atom.
This can be easily found through the electronic configuration of atom.
Electronic configuration of F:
F₉ = 1s² 2s² 2p⁵
We can see that the valence electrons are present in second energy level of F atom.
There are seven valence electrons of fluorine.
It is called halogens.
Halogens are very reactive these elements can not be found free in nature. Their boiling points also increases down the group which changes their physical states. i.e fluorine is gas while iodine is solid.
Fluorine:
1. it is yellow in color.
2. it is flammable gas.
3. it is highly corrosive.
4. fluorine has pungent smell.
5. its reactions with all other elements are very vigorous except neon, oxygen, krypton and helium.
