knowverseQuestion 1
What is a period?
Periods run horizontally across the table.
Source excerpt
A period is simply a horizontal row that runs across the table, much like a single week on a wall calendar.
From the Knowverse course text.
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Reading rows, columns and families
The periodic table orders elements by atomic number, the number of protons in the nucleus. Horizontal rows are periods, while vertical columns are groups. Elements within a group often show related chemical behaviour. This organization helps chemists compare elements and look for patterns rather than treat each one as unrelated.
Metals typically conduct heat and electricity and can be shaped without shattering. Solid nonmetals often behave differently, while metalloids have intermediate properties. Silicon is a familiar semiconductor. These categories describe patterns rather than an exception-free checklist: hydrogen, for example, is a nonmetal even though it appears above the alkali metals.
Source excerpt
While rows are periods, the vertical columns that run from top to bottom are called groups.
From the Knowverse course text.
Electrons and chemical behaviour
Valence electrons occupy the outer part of an atom and help determine its chemical behaviour. Alkali metals belong to Group 1, halogens to Group 17 and noble gases to Group 18. Noble gases are relatively unreactive under ordinary conditions, while alkali metals and halogens readily form many compounds.
Ionization energy measures the energy needed to remove an electron from an atom. Electronegativity describes attraction for shared electrons in a bond. They measure different situations. Inner electrons also shield outer electrons from some nuclear attraction, helping explain why atomic size and electron-removal energy change across the table.
Source excerpt
Ionization energy is the specific amount of energy required to remove one electron from a neutral atom.
From the Knowverse course text.