Answer:
it means positive and negative charges are equal.
Explanation:
An atom consist of electron, protons and neutrons. Protons and neutrons are present with in nucleus while the electrons are present out side the nucleus.
All these three subatomic particles construct an atom. A neutral atom have equal number of proton and electron. In other words we can say that negative and positive charges are equal in magnitude and cancel the each other. For example if neutral atom has 6 protons than it must have 6 electrons. The sum of neutrons and protons is the mass number of an atom while the number of protons are number of electrons is the atomic number of an atom.
when a neutral atom loses a electron positive charge is created because number of protons are positive charge becomes greater than negative charge.
X → X⁺ + e⁻
When a neutral atom accept the electron negative charge is created because negative charge is become greater than positive charge.
X + e⁻ → X⁻
Answer:
The number of moles =

The number of molecules =

Explanation:
Volume of the sphere is given by :

here, r = radius of the sphere


Radius = 3 mm
r = 3 mm
1 mm = 0.01 dm (1 millimeter = 0.001 decimeter)
3 mm = 3 x 0.01 dm = 0.03 dm
r = 0.03 dm
<em>("volume must be in dm^3 , this is the reason radius is changed into dm"</em>
<em>"this is done because 1 dm^3 = 1 liter and concentration is always measured in liters")</em>



(1 L = 1 dm3)
Now, concentration "C"=
The concentration is given by the formula :

This is also written as,

moles
One mole of the substance contain "Na"(= Avogadro number of molecules)
So, "n" mole of substance contain =( n x Na )

Molecules =

molecules
Explanation:
1.
i. Measure the initial volume of water in a graduated cylinder.
ii. Now submerge the irregularly shaped metal into water in a graduated cylinder.
iii. Measure the final volume of water.
iv. The difference between the final volume and the initial volume is the volume of the irregularly shaped metal.
2.
When adding the irregularly shaped metal into the glass graduated cylinder. Make sure that the irregularly shaped metal is completely submerged into the water.
Nobody specifically made the periodic table but it was first thought of by Dmitri Mendeleev in 1869.