Atomic size decreases across a period due to an increase in the effective nuclear charge. true or false

True

Explanation:

Along a period from left to right  the atomic size decreases because all the electrons are subsequently added to the same shell, also the equal no. of protons are added to the nucleus leading to the increase in the net effective nuclear charge at the constant distance. This leads to the increase in the force of attraction between the (opposite) charged particles which shrinks the atomic size.

when heated, the valance electrons increased their speed and transferred the heat from electron to electron.   i just took the test.