Atoms and Subatomic Particles
What are the three main subatomic particles?
Protons, neutrons and electrons
For an atom to become an ion, it can ______ or lose electrons.
gain
What does the atomic number represent?
number of protons
What type of reaction joins two elements together to form one compound?
Synthesis
Balance:
H₂ + Cl₂ → HCl
H₂ + Cl₂ → 2HCl
Where are protons and neutrons found?
Nucleus of the atom
An atom has an electron configuration of 2,6. This would be an atom of..
oxygen
Which group contains very reactive metals?
Group 1 (alkali metals)
In a decomposition reaction, what happens?
One reactant breaks down into simpler substances
Balance:
Na + O₂ → Na₂O
4Na + O₂ → 2Na₂O
What is the mass number?
number of protons + neutrons
What would be the electron configuration for an atom of Aluminium?
2,8,3
Which side of the periodic table contains non-metals?
Right side
What type of reaction occurs when one element replaces another element in a compound?
Single replacement
Why must chemical equations be balanced?
Because of the law of conservation of mass — atoms cannot be created or destroyed.
An element has an atomic number of 15 and a mass number of 31.
How many neutrons does it have?
16
What would an atom in Group 7 do to form a stable configuration?
Gain one electron
Why are elements in the same group chemically similar?
Same number of valence electrons
What type of reaction is this?
Na₂S + 2HCl → 2NaCl + H₂S
Explain why it fits that category.
Double replacement
Two compounds exchange elements
Na₂S and HCl swap partners → NaCl and H₂S
Balance:
Al + O₂ → Al₂O₃
4Al + 3O₂ → 2Al₂O₃
An atom of element X has 20 protons, 18 electrons and 22 neutrons.
Identify the element, and state its charge
Calcium 2+
What is the electron configuration of an Oxygen Ion (O2-)
2,8
Explain why elements get more reactive as you go down Group 1.
Outer electron is further from the nucleus → weaker attraction → easier to lose
A compound AB reacts with CD to produce AD and CB.
Identify the type of reaction.
Double replacement
Balance the combustion of ethanol:
C₂H₅OH + O₂ → CO₂ + H₂O
C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O