Scientific notation in standard form

Take the number of the exponent and move the decimal that many places.  If it is positive move it left and if it is negative move it right.

For Example:

2.57x10³= 2570

Fill in any access spaces with zero.

Taking that same number to the negative 3 power

2.57x10^-3

0.00257

I put a 0. to show it is a distinctive decimal.

i believe it is-

d.) gravity pulled particles of dust and gas together to form planets.

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.