Atoms, Elements, and the Periodic Table

Flashcards covering the history of atomic theory, the organization of the periodic table, and the classification of elements, molecules, and compounds.

The Ancient Greek philosopher Democritus used the word __________ to describe particles that could not be divided up any further.

atomos

Unlike modern scientists, Democritus was a natural philosopher who proposed hypotheses based on __________.

thought and reasoning

In the 1780s, French chemist __________ and his wife Marie-Anne Lavoisier were convinced that matter could not be created or destroyed.

Antoine Lavoisier

In 1810, the English scientist __________ became the originator of what is now called the atomic theory.

John Dalton

John Dalton assigned comparison weights to atoms by comparing them to the lightest atom, which is __________.

hydrogen

In 1865, John Newlands published a paper describing how atoms could be arranged into groups of eight with similar properties, a concept he called the __________.

Law of Octaves

The Russian scientist Dmitri Mendeleev organized atoms into a table that allowed him to predict the properties of __________.

atoms that had not yet been discovered

The modern __________ identifies elements in order of their atomic number and groups them by similar properties.

periodic table

An __________ is a pure substance made of only one type of atom and cannot be broken down into other substances.

element

There are __________ different elements that are found naturally on Earth.

94-98

In their solid state, the atoms of metals are held together in a structure called a __________.

lattice

Gases like neon and helium are __________, meaning each gas particle consists of a single atom.

monatomic

Gases such as oxygen, hydrogen, and nitrogen exist as __________, where atoms move together in pairs.

diatomic molecules

The vertical columns in the periodic table are called __________, while the horizontal rows are called periods.

groups

A __________ is formed when two or more atoms are linked or bonded together.

molecule

A molecular __________ contains atoms of two or more different elements, such as carbon dioxide ($CO_2$).

compound

In a chemical formula, the __________ after an element symbol (e.g., the 2 in $H_2O$) tells you how many atoms of that element are present.

subscript

Compounds that consist of long strings of repeating atoms, such as plastics, starch, and proteins, are called ___________.

polymers

In a chemical reaction, the starting substances that have their bonds broken are called __________.

reactants

Food additives such as antioxidants and __________ are used to improve appearance and increase shelf life.

preservatives