Topic1 Key Concepts In Cehmsitry Flashcards
What are the relative mass and relative charge of:
Proton
Neutron
Electron
Proton:
Relative mass:1
Relative charge:+1
Electron:
Relative mass:
Relative charge:-1
Neutron:
Relative mass:1
Relative charge:+1
Where are protons and electrons and neutrons located?
Protons:nucleus
Neutrons:nucleus
Electrons:around nucleus in shells
What are atoms neutral?
Because they have equal number of protons and electrons and so charges cancel out making the charges 0
What is the atomic number and mass number?
How calculate the neutrons?
Atomic number:protons
Mass number:protons+neutrons
Neutrons:mass number-atomic number
What are isotopes?
Different forms of the same element
Same number of protons and different number of electrons
How do you work out relative atomic mass of an element?
Multiply each relative isotopic mass by its isotopic abundance
Add them up
Divide by sum of abundance
Give two differences and 1similaritiy in Mendeleev periodic table to the one today?
Differences:
Gaps in Mendeleev compared to today
Mendeleev sorted elements in order of atomic mass
Today’s one sorted elements in order of atomic number
Similarities:both periodic table was laid out in similar properties
What is the maximum amount of electrons filled in the 1st,2nd and 3rd shell?
1st-2 electrons
2nd-8 electrons
3rd-8 electrons
What are ions?
What is an anion?
What is cation?
Ion-single atoms or groups of atoms
Anion-when atoms gain electrons
Cation-when atom loses electrons
What do group 1 and 2 elements do to form positive ions?
What do group 6 and 7 elements do to form negative ions?
Lose electrons
Gain electrons
What is the overall charge of an ionic compound?
Why?
0
Because all negative charges must balance all the positive charges
What is ionic bonding?
The transfer of electrons that is held by ionic bonds that are electrostatic forces
What are the properties of ionic compounds?
High melting and boiling point:due to strong attractions between the ions
Don’t conduct electricity in a solid:due to ions in fixed place and can not move.
Conduct electricity when melted:ions free to move and so carry current
Conduct electricity when dissolved in water:ions are separate and free to move in solution so carry current.
What is a covalent bond?
A strong bond that forms when pair of electrons is shared between two atoms
What are properties of simple molecular compounds?
Atoms within the molecules are held by strong covalent bonds
Don’t conduct electricity:don’t contain any free ions
Low boiling and melting point:weak intermolecular forces break down easily