More subatomic particles, more mass
Many properties change as you move from left to right on the periodic table. For example: atomic number increases; electronegativity increases; atomic radii decrease etc. etc.
As you move left to right on the periodic table, the number of valence electrons an element has increases. The number of valence electrons an element has corresponds to which group (column) an element is. (This rule does not apply to transition metals...)
Non-metals are placed at the right hand side of the periodic table.
Increasing (valance) electrons.
When you move from left to right on the periodic table, the atomic number of the elements increase.
The melting temperature properties generally change as you go from left to right in the periodic table by going down/decreasing.
The melting temperature properties generally change as you go from left to right in the periodic table by no specific trend/no detail pattern.
If you mean the repeating pattern from left to right that occurs in the Periodic Table of the Elements, it is called the Law of Octaves. This is because the pattern of periodicity occurs in groups of eight.
Going Up
it is a chemical change! (sexy right?;)
Yes, elements generally change from metals to non-metals from left to right across the periodic table. In the periodic table, elements are arranged in order of increasing atomic number, and as you move across a period from left to right, the properties of the elements change from metallic to non-metallic. The left side of the periodic table consists of metals, the middle consists of metalloids, and the right side consists of non-metals.
Electronegativity generally increases from left to right across a period and decreases down a group in the periodic table. This trend occurs because elements on the right side of the periodic table have a greater ability to attract electrons due to increased nuclear charge and effective nuclear charge.