Fundamental ideas in chemistry Flashcards
What is the nucleus?
- Middle of an atom
- Contains protons and neutrons
- Has a positive charge due to protons
What charge are protons?
Positive
What charge are neutrons?
Don’t have a charge
What are electrons?
- Move around the nucleus
- Negative charge
- Tiny
- Occupy shells around the nucleus
What charge does an atom have overall?
No charge!
( The charge on electrons is the same size as those on protons but opposite; the number of protons always equals the number of electrons in an atom)
What is an ion?
When an atom loses or gains electrons, giving it a charge
What is an element?
A substance consisting of one type of atom only
What gives the indication for the type of atom it is?
The proton number- the number of protons in the nucleus
How many elements are there (roughly)?
100
What is an atom?
A cluster of sub-particles (protons, neutrons,electrons) which cannot be divided; the smallest part of an element which retains its chemical properties
What force holds the sub-particles together in the nucleus?
The “strong force”
What are the atomic mass units of each sub-particle?
- Proton = 1
- Neutron = 1
- Electron = 0 (negligible mass)
What are the vertical columns of the periodic table and what do they tell us?
Groups: define element groups, same outer shell electron arrangement- this is why elements in the same group have similar properties
What are periods in the periodic table; what do they tell us?
Signifies the highest un-exited energy level for an electron in that element
What are the different groups of the periodic table? (Generally)Most reactive to least reactive
1- Alkali metals e.g. sodium, potassium
2- Alkali earth metals e.g. magnesium, calcium
- Transition elements- e.g. most metals, iron, copper
3,4,5,6- Non-metals e.g. nitrogen, oxygen
7- Halogens e.g. fluorine, chlorine
0- Noble gases e.g. helium, argon
What does inert mean?
Something that isn’t readily reactive with other elements, forming few or no chemical compounds (inactive)
Why are the noble gases inert?
Their outer electron shells are already “full” (the more empty an outer shells is, the more reactive it is)
e.g. why is potassium more reactive than lithium?
- Both need to lose an electron to have full outer shells
- Potassium has more shells away from positive attraction of the nucleus making it more reactive
e.g. why is sodium more reactive than magnesium?
- Sodium must lose one electron to have a full outer shell
- Magnesium must lose two electrons to have a full outer shell
- The latter takes more energy meaning sodium is more volatile and reactive
What are the 5 rules about electron shells?
1- Electrons always occupy shells (energy levels)
2- The lowest energy levels are always filled first from closest to the nucleus out
3- Only a certain number of electrons can occupy each cell
4- Atoms are happier when they have full electron shells
5- In most atoms the outer shell is not full meaning that the atom will ‘want’ a reaction to take place to fill it
How many electrons are allowed in each shell?
1- 2
2- 8
3- 8
What are the two ways of bonding atoms?
Ionic and covalent
What does making bonds between atoms involve?
- Involves atoms giving away, taking or sharing electrons
- The nuclei is not involved as that would change the element- only electrons
What is ionic bonding?
A compound formed from a metal and a non-metal consisting of ions which strongly attract
What is covalent bonding?
- 2 non- metals (same or different atoms)
- Both need to gain electrons to form a full outer shell of electrons
- Electrons shared in pairs
- In each shared pair there can be one or more electrons shared
What are some examples of ionic and covalent bonding?
Ionic e.g. magnesium oxide, lithium chloride
Covalent e.g. water, oxygen
