A 2.1

What is the main purpose of the periodic table?

To organize all known elements according to their chemical properties.

What are the three major categories of elements in the periodic table?

Metals, non-metals, and metalloids.

What physical properties are associated with metals?

Metals have a shiny lustre, are good conductors of heat and electricity, are malleable and ductile, and are solids at room temperature except for mercury.

What characterizes nonmetals?

Nonmetals are dull, poor conductors of heat and electricity, brittle, and can be solid, liquid, or gas at room temperature.

What are metalloids?

Metalloids have characteristics of both metals and nonmetals, and conduct electricity but not as well as metals.

Who invented the first periodic table and in what year?

Dimitri Mendeleev in 1872.

What did Mendeleev's periodic table organize elements by?

By their properties.

What is the significance of the atomic number of an element?

It indicates the number of protons in an atom and determines the element's identity.

What is mass number?

The mass number is the total number of protons and neutrons in an atom's nucleus.

What are isotopes?

Atoms of the same element that have different numbers of neutrons.

What is the atomic mass unit (amu)?

A unit used to express the mass of atoms, based on the mass of carbon-12.

What is ionization?

The process of gaining or losing electrons to form an ion.

What is a cation?

A positively charged ion formed when a metal atom loses electrons.

What is an anion?

A negatively charged ion formed when a non-metal atom gains electrons.

What does the octet rule state?

Atoms tend to gain, lose, or share electrons to achieve eight electrons in their outer shell.