Periodic Table History & Layout
This scientist organized the first useful periodic table by increasing atomic mass.
Who was Dmitri Mendeleev?
This ancient Greek philosopher coined the term "atomos" for a tiny piece of matter that cannot be divided.
Who was Democritus?
These are the specific electrons located in an atom's outermost energy level that determine chemical properties.
What are valence electrons?
The elements on the periodic table are broadly classified into three main categories: metals, nonmetals, and these.
What are metalloids?
This unit of measurement is defined as exactly one-twelfth the mass of a carbon-12 atom.
What is an atomic mass unit (amu)?
Mendeleev’s periodic table was confirmed to be useful because it allowed scientists to accurately predict the properties of these.
What are undiscovered (or unknown) elements?
This subatomic particle carries a negative charge and orbits outside the nucleus.
What is an electron?
As you look at main group elements from left to right across any single period, the number of valence electrons does this.
What is increases?
This element is the structural backbone of almost all organic compounds in your body, with the exception of water.
What is Carbon?
Phosphorus is one block to the left of Sulfur. If Sulfur's atomic number is 16, this is the atomic number of Phosphorus.
What is 15?
This is the scientific term for a horizontal row on the periodic table.
What is a period?
In this scientist's atomic model, electrons travel in fixed paths around the nucleus like planets orbiting the sun.
What is the Bohr model?
This column on the far-left of the periodic table contains the most reactive metals.
What is Group 1A (or the Alkali Metals)?
Unlike silver, the metalloid Silicon is a semiconductor, meaning it conducts an electric current much better than this nonmetal from Group 6A.
What is Sulfur?
To determine the official atomic mass of an element, scientists calculate this type of average of its natural isotopes.
What is a weighted average?
As you move from left to right across a horizontal period, properties change from being highly metallic to this.
What is nonmetallic?
To find the number of neutrons in an atom, you subtract the atomic number from this other number.
What is the mass number?
Within the highly reactive Group 1A elements, this specific metal is the most reactive of the choices , also known as (Cs).
What is Cesium (Cs)?
Sodium, chromium, and copper all belong to this single structural classification of elements.
What are metals?
These specific commercial lights can contain any noble gas, such as helium or argon, to emit different glowing colors.
What are "neon" lights?
Properties of elements repeat in a predictable pattern when you move from this to this on the table.
What is row to row (or period to period)?
An electron must do this to its energy level in order to jump to a higher, excited energy state.
What is gain (or absorb) energy?
Unlike alkali metals, the reactivity of the Group 7A Halogens actually increases as you move in this direction up the column.
What is upward?
Because they are highly reactive, alkali metals and halogens are almost never found alone in nature; they are only found as these.
What are compounds (or salts)?
If an element has an atomic number of 36 and an atomic mass of 83.80, it is this specific noble gas.
What is Krypton (Kr)?