An atom has the following electron configuration.

1s22s22p63s23p64s23d3

how many valence electrons does this atom have?

a.2
b.3
c.5
d.11

5

Explanation: add up all the electrons and it will amount to 23. Arranging by the old model for electronic configuration, we have : 2, 8, 8, 5

The last number being 5 represent its valence electron

vanadium has 5 valence electrons

Explanation:

The element with electron configuration 1s2 2s2 2p6 3s2 3p6 4s2 3d3

has 23 electrons. This element is Vanadium.

For Vanadium, the atomic number is 23 and the electronic configuration given is  

1s2 2s2 2p6 3s2 3p6 4s2 3d3

Vanadium's ground state electron configuration is [Ar] 3d3 4s2.

Thus vanadium has 5 valence electrons and during ionic bonding, s-shell electrons are lost first and than d-shell electrons would be lost.

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.

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.