Topic 1 - Atoms, Molecules, Isotopes and Ions Flashcards
All the different substances in the world are made from fundamental materials called_______________
Elements
What is an element?
An element is a:
- substance
- which cannot be split into 2 or more simpler substances
- by chemical means.
How is every element unique?
Because every element has its own name and symbol.
Eg. Lithium = Li,
Magnesium = Mg
All elements are made of many small particles called:
ATOMS
In any one element, all the atoms are _______________.
The atoms of each element are unique because ___________________.
In any one element, all the atoms are identical to each other, but different from all other elements (in size and mass).
Each element has its own type of atoms.
Because the atoms of each element have a different size and mass from the other elements.
What is an Atom?
An atom is the SMALLEST particle of an element.
It has the symbol of the element.
How do you represent Atoms?
- Circles (different size and symbols)
- Ball and stick modles - spheres connected by sticks
How can you see an atom?
Using an electronic microscope.
What are the particles in an Atom?
Sub-atomic particles called:
- Protons;
- Neutrons; and
- Electrons
What do Protons and Neutrons make up?
The Nucleus of the Atom.
What is the symbol, charge and relative mass of a proton?
Symbol = p
Relative Electric Charge = +1
Relative mass = 1
What is the symbol, charge and relative mass of a Neutron?
Symbol = n
Relative Electric Charge = 0
Relative mass = 1
What is the symbol, charge and relative mass of an Electron?
Symbol = e
Relative Electric Charge = - 1
Relative mass = 1/1840
Every element has its own Atomic Number and Mass Number.
How do you indicate the Atomic Number and
Mass Number of an element?
What is an Mass Number of an element?
Mass Number =
Total Number of
Protons + Neutrons
What is an Atomic Number of an element?
Atomic Number = Number of protons
Notes:
- It is the proton number that identifies an element.
- The number of protons differentiates atoms of one element from the atoms of another element.
- The elements in the Periodic Table are arranged in order of the number of Protons.
- The number of protons in the atoms of an element is FIXED.
- A change in the number of protons will change the element.
How do you find the number of electrons in an element?
The number of electrons = The number of Protons = Atomic Number (bottom)
So the number of electrons = Atomic Number also
How do you find the number of neutrons in an element?
Mass Number = Number of protons + Neutrons
Number of Neutrons = Mass Number - Number of Protons
What is the charge of all atoms?
All atoms are electrically NEUTRAL, meaning NO overall charge
(because number of protons = number of electrons)
What is involved in a chemical reaction?
In a chemical reaction, it is the ELECTRONS,
and not the protons or neutrons
that are involved in the reaction.
What is the number of electrons in the
outermost valence shell
within each group of the Periodic Table?
How are electrons placed?
They are placed in electron shells
surrounding the nucleus (protons and neutrons).
1st shell = max 2 electrons
2nd shell = max 8 electrons
3rd shell = max 8 electrons
What is an ion?
An ion is a charged atom or molecule.
It is charged because the
number of electrons do not equal the number of protons
in the atom or molecule.
What is a positive ion called?
A Positive Ion is called CATION (read cat-ion).
See example of Sodium and Magnesium atoms and cations:
How is Sodium ion formed from Sodium atom?
How is Magnesium ion formed from Magnesium atom?
Sodium atom (2:8:1) loses 1 electron (1e) to form Sodium ion (2:8)
Na - 1e = Na+
Magnesium atom (2:8:2) loses 2 electrons (2 e) to form Magnesium ion (2:8)
Mg - 2e = Mg2+
What is a negative ion called?
Negative ion is known as ANION (read as “an-ion”).
See example of Chlorine and Oxygen atoms and cations:
How is Chlorine ion formed from Chlorine atom?
How is Oxygen ion formed from Oxygen atom?
Chlorine atom (2:8:7) gains 1 electron (1e) to form chloride ion (2:8:8)
Cl + 1e = Cl-
Oxygen atom (2:6) gains 2 electrons (2 e) to form Oxygen ion (2:8)
O + 2e = O2-
What are Isotopes?
Isotopes are atoms of the same element.
They have the same number of Protons (therefore same element),
but different numbers of Neutrons in their nuclei (hence isotopes).
What are the similarities and differences between Isotopes?
Similarities:
- Similar Atomic Number (since proton # same)
- Similar number of protons;
- Similar number of electrons (since p # = e #)
- Similar chemical properties
Differences:
- Different number of neutrons;
- Hence different mass number (since Mass # = p + n);
- Different physical properties (eg diffusion rate, density, mass, etc.)
Working example of Hydrogen/ Deuterium/ Tritium:
Atomic # =
Number of p =
Mass # =
Number of n =
Hydrogen:
Atomic # =
Number of p =
Mass # =
Number of n =
Deuterium:
Atomic # =
Number of p =
Mass # =
Number of n =
Tritium:
Atomic # =
Number of p =
Mass # =
Number of n =
What is a molecule?
A Molecule is a group of 2 or more atoms chemically joined together.
What is a diatomic molecule?
What are common examples?
Diatomic molecules are simple molecules made of 2 atoms chemically joined together.
Most non-metallic elements consist of diatomic molecules.
What is a carbon dioxide molecule made of?
A chemical combination of carbon and oxygen atoms –
Each molecule would look like this: OCO
What is the difference between the molecules of an element v
the molecules of a compound?
Molecules of element: consist of fixed number of 1 kind of atoms
Molecules of compounds: consists of a fixed number of 2 or more different kinds of atoms
How can you represent the molecule by a chemical formula?
The formula will show:
- the number of elements present;
- the number of atoms of each element present.
