How does metallic character vary across a period?

Metallic character decreases across a period from left to right on the periodic table.

In more detail, the metallic character of an element refers to its ability to lose electrons and form positive ions, which is a characteristic property of metals. As you move across a period from left to right on the periodic table, the metallic character of the elements decreases. This is due to the increase in nuclear charge, which pulls the electrons closer to the nucleus, making it more difficult for the atom to lose electrons and thus decreasing its metallic character.

At the start of a period, you have the alkali metals which are very reactive and have a strong tendency to lose electrons, hence they have a high metallic character. As you move across the period, the elements become less metallic and more non-metallic. This is because the number of protons in the nucleus increases, which increases the positive charge of the nucleus and pulls the electrons closer. This makes it harder for the atom to lose an electron, which is a characteristic of metals.

By the time you reach the end of a period, you have the noble gases which are very unreactive and have a low tendency to lose electrons, hence they have a low metallic character. In fact, they are so unreactive that they are often referred to as inert gases. This trend of decreasing metallic character across a period is consistent across all periods of the periodic table.

In summary, as you move across a period from left to right on the periodic table, the metallic character of the elements decreases. This is due to the increase in nuclear charge, which pulls the electrons closer to the nucleus, making it more difficult for the atom to lose electrons. This trend is consistent across all periods of the periodic table.