What is all matter made of in chemistry?
Atoms.
What is the smallest unit of an element that keeps its properties?
The atom.
How is each element shown on the Periodic Table?
By a unique chemical symbol.
What are the two particles in the nucleus of an atom?
Protons and neutrons.
Where are electrons found in the atom?
In energy levels/shells around the nucleus.
What does the atomic number tell you?
Number of protons.
How do you calculate neutrons in an atom?
Neutrons = mass number − atomic number.
In a neutral atom, how do electrons compare to protons?
Electrons equal protons.
What was Mendeleev’s main achievement?
He arranged elements by properties and left gaps for undiscovered ones.
Why did Mendeleev’s table gain acceptance?
His predictions about new elements were later confirmed.
For the first 20 elements, what is the electron arrangement pattern?
2, 8, 8, 2.
When drawing an atom, where do protons and neutrons go?
In the nucleus.
When drawing an atom, where do electrons go?
In shells around the nucleus.
How do you use the Periodic Table to find protons?
Read the atomic number.
How do you use the Periodic Table to find electrons in a neutral atom?
Electrons = atomic number.
Which group is called alkali metals?
Group 1.
Which group is called alkaline earth metals?
Group 2.
Which group is called transition metals?
Central block, Groups 3–12.
Which group is called halogens?
Group 17.
Which group is called noble gases?
Group 18.
How does reactivity change down Group 1 metals?
Reactivity increases.
Why are Group 1 metals so reactive?
They lose their one valence electron easily.
How does reactivity generally change down Group 17 halogens?
Reactivity decreases.
Why are halogens reactive?
They need one electron to fill the outer shell.
