Atoms

FOR QUIZ AND CHECKPOIND

Atom

The basic unit of matter, consisting of a nucleus surrounded by electrons.

Nucleus

The central part of an atom, containing protons and neutrons.

Proton

A positively charged particle located in the nucleus of an atom.

Neutron

A neutral particle located in the nucleus of an atom, contributing to the atomic mass.

Electron

A negatively charged particle that orbits the nucleus of an atom.

Atomic number

The number of protons in the nucleus of an atom, which defines the element.

Isotope

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Molecule

A group of two or more atoms bonded together, representing the smallest unit of a chemical compound.

Element

A pure substance that cannot be broken down into simpler substances by chemical means and is made up of only one type of atom.

Compound

A substance formed when two or more different elements are chemically bonded together.

Chemical bond

The force that holds atoms together in a molecule or compound.

Valence electrons

Electrons in the outermost shell of an atom that are involved in chemical bonding.

Cation

A positively charged ion formed when an atom loses one or more electrons.

Anion

A negatively charged ion formed when an atom gains one or more electrons.

Periodic table

A tabular arrangement of all known elements organized by increasing atomic number and by their chemical properties.

Atomic mass

The weighted average mass of an element's isotopes, measured in atomic mass units (amu).

Octet rule

A chemical rule of thumb that states atoms tend to combine in such a way that they each have eight electrons in their valence shell, achieving a stable electron configuration similar to that of noble gases.

Period

A horizontal row in the periodic table, indicating elements with increasing atomic numbers and similar energy levels.

Group

A vertical column in the periodic table, indicating elements that exhibit similar chemical properties and have the same number of valence electrons.

Electronegativity

A measure of the tendency of an atom to attract a bonding pair of electrons, indicating how strongly an atom can attract electrons in a bond.

Covalent bond

A type of chemical bond formed when two atoms share one or more pairs of electrons to achieve a full outer shell of electrons.

Ionic bond

A type of chemical bond formed between two atoms when one atom transfers electrons to another, resulting in the formation of oppositely charged ions that attract each other.

Formula to find neutrons

The number of neutrons in an atom can be found using the formula: Neutrons = Atomic Mass - Atomic Number.

Dmitri Mendeleev

A Russian chemist who created the first version of the periodic table, organizing elements by increasing atomic mass and grouping them by similar properties in 1869.

Periodic table development

The periodic table was developed over time, with contributions from various scientists like Mendeleev and Moseley, who reorganized it based on atomic number instead of atomic mass to correct inconsistencies.