These horizontal rows run from left to right across the periodic table.
What are periods?
Most elements on the periodic table belong to this classification.
What are metals?
Lithium, sodium, and potassium belong to this highly reactive family.
What are the alkali metals?
This subatomic particle determines an element’s atomic number.
What is a proton?
This is the chemical symbol for oxygen.
What is O?
These vertical columns contain elements with similar chemical properties.
What are groups?
These elements are generally located on the right side of the periodic table.
What are nonmetals?
Helium, neon, and argon belong to this mostly unreactive family.
What are the noble gases?
These are the electrons in an atom’s outermost occupied energy level.
What are valence electrons?
This is the chemical symbol for potassium.
What is K?
Elements are arranged in increasing order according to this number.
What is atomic number?
These elements have properties of both metals and nonmetals.
What are metalloids?
Fluorine, chlorine, and bromine belong to this family of reactive nonmetals.
What are the halogens?
In a neutral atom, the number of electrons equals the number of these particles.
What are protons?
This element has the symbol Na.
What is sodium?
An element in Period 3 has this many occupied electron energy levels.
What are three energy levels?
Metalloids are generally located along this line on the periodic table.
What is the stair-step line?
Oxygen, sulfur, and selenium belong to this periodic-table group.
What is Group 16, or the oxygen family?
Two Bohr models have the same number of outermost electrons. This is the best prediction about the elements.
What is that they have similar chemical properties?
Sodium explodes when placed in water. Because this element is also in Group 1, it should behave similarly.
What is potassium?
Element X has atomic number 19, while the element beside it has atomic number 20. This describes X’s position compared with element 20. Are they in the same group or the same period? Do they have similar properties?
Most metals have this state of matter at room temperature. What is the state of matter and what it the exception?
The state is solid, mercury is an exception.
Members of the same chemical family behave similarly because they usually have the same number of these electrons.
What are valence electrons?
An atom with a full outer energy level will generally have this level of chemical reactivity.
What is low reactivity, or be unreactive?
This formula represents a molecule containing two hydrogen atoms and one oxygen atom.
What is H₂O?