Most of an atom's mass is located in this central core.
What is the nucleus?
100
The periodic table we use today has every known element arranged in order according to this, the number of protons per atom.
What is the atomic number?
100
This element with four valence electrons is appropriately enough, the first member of the carbon family.
What is carbon?
100
Oxygen
What is O?
100
The number of protons in an atom of copper (Cu).
What is 29?
200
Of the three main subatomic particles (protons, neutrons and electrons) it is the one that lacks an electrical charge.
What are neutrons?
200
The periodic table is organized into this many vertical columns known as groups or families.
What is seventeen?
200
This family of metals, found in the first column of the periodic table, reacts violently with water.
What are alkali metals?
200
Nitrogen
What is N?
200
The number of electrons in an average atom of silver (Ag).
What is 47?
300
Every atom has between one and seven of these regions where fast-moving electrons can be found.
What are shells?
300
The periodic table has elements arranged into seven horizontal rows called by this name.
What are periods?
300
This family of gases found in group 18 almost never reacts with other elements because its atoms already have complete valence shells.
What are the noble gases?
300
Silicon
What is Si?
300
The number of neutrons in an average atom of potassium (K).
What is 20?
400
Sometimes these electrons, which are furthest out from the center of the atom, can be shared with other atoms.
What are valence electrons?
400
While periodic tables sometimes list elements with atomic numbers as high as 118, this element with an atomic number of 92 is the heaviest one found in nature.
What is uranium?
400
Elements like chlorine found in this group 17 family are called by this name meaning "salt" because they are often found in salts such as sodium chloride, also known as table salt.
What are halides?
400
Magnesium
What is Mg?
400
The number of electron shells in an atom of lead (Pb)?
What is six?
500
Even though matter seems pretty solid, experiments have proven that atoms contain mostly this.
What is empty space?
500
The first periodic table was developed in 1869 by this Russian scientist.
Who is Dmitri Mendeleev?
500
Elements in this family such as calcium and magnesium are often important nutrients found in the foods we eat.
What are alkaline earth metals?
500
Sodium
What is Na?
500
The number of valence electrons in an atom of Indium (In).