The atomic mass increases as you move across or down the table because the mass is calculated by adding up the protons and neutrons in each element’s atom. The number of protons increases with each element, which means the weight goes up, as well. Electrons are not included in the atomic mass, as they contribute much less to the atom’s weight than protons and neutrons.
For example, the first row contains Hydrogen, which has an atomic number of 1, and Helium, which has an atomic number of 2. However, they are at opposite ends of the table, as they are in different groups.
Most elements fall into 1 group, but Hydrogen can be placed with the Halogen family or the Alkali Metals. On some charts, it will appear with both. In most cases, the columns will be numbered 1-18, either above or below the table. The numbers may be shown in Roman numerals (IA), Arabic numerals (1A), or numerals (1). When you go down a group from top to bottom, it’s called “reading down a group. ”
For example, the first 3 rows have gaps, as the Transition Metals don’t appear on the table until atomic number 21. Similarly, elements 57 through 71, which are the Rare Earth Elements, are usually pictured as a subset at the bottom right of the table.
For example, the elements in the period 1 have 1 orbital, while the elements in period 7 have 7 orbitals. In most cases, they’re numbered 1-7 down the left hand side of the table. When you move across a row from left to right, it’s called “reading across a period. ”
Keep in mind that hydrogen can be grouped with either the Halogens or the Alkali Metals because of its properties, so it may appear on either side of the table or may be colored differently. Elements are labeled as a metal if they have luster, are solid at room temperature, conduct heat and electricity, and are malleable and ductile. Elements are considered a non-metal if they lack luster, don’t conduct heat or electricity, and are non-malleable. These elements are usually gases at room temperature but may also become a solid or liquid at certain temperatures. Elements are labeled as semi-metals if they have a mixture of properties of both metals and non-metals. [7] X Research source
This symbol is usually derived from the Latin form of the element’s name, but it may be derived from the widely accepted common name, especially for newer elements. For example, the symbol for Helium is He, which closely resembles the common name. However, the symbol for Iron is Fe, which is harder to recognize at first.
Some periodic tables may omit the full name, using just the symbol.
The atomic number will be a whole number, not a decimal.
You’ll use the atomic number to find the number of electrons and neutrons as well!
Ions are electrically charged. If an ion has more protons, it is positive, which is indicated with a positive sign next to the ion’s symbol. If it has more electrons, the ion is negative, which is indicated with a negative symbol. You will not see a plus or minus symbol if the element is not an ion.
Because the weights are averaged, most elements will have atomic weights that include decimals. Although it may appear as though the atomic weight increases in number from top left to bottom right, this is not true in all cases.
For example, the atomic weight of Carbon is 12. 011, which rounds to 12. Similarly, the weight of Iron is 55. 847, which rounds to 56.
Use this formula: Neutrons = Mass Number - Protons For example, Carbon’s mass number is 12, and it has 6 protons. Since 12 - 6 = 6, you know Carbon has 6 neutrons. For another example, Iron’s mass number is 56, and it has 26 protons. Since 56 - 26 = 30, you know Iron has 30 neutrons. An atom’s isotopes will contain a different number of neutrons, which changes the atom’s weight.
