1 Flashcards
What is an atom?
the smallest unit of matter and is the smallest part of an element that can exit (only one)
What is an element?
a substance made from one type of atom
- all listed in periodic table - about 100
What determines the element?
The number of protons/ atomic number
What is the atomic or mass number?
- Small number = atomic number (number of protons and electrons)
- Bigger number = mass number (sum of neutrons and protons)
What is inside the nucleus and what are their charges?
Protons - positive (relative mass of 1)
Neutrons - neutral (relative mass of 1)
What orbits around the nucleus in shells?
Electrons - negative charge (has relative mass of 0- no mass)
Why do atoms have no overall charge?
protons have positive, electrons have negative charge – these 2 are equal to each other so cancel each other
What is an ion?
when atoms lose/gain electrons the charges of protons and electrons will no longer be equal and the atom overall charge will be changed. == a charged atom/molecule
How can you work out ions charge?
- If an atom loses 1 electron, it becomes 1+ ion
- If an atom gains 1 electron, it becomes 1- ion
-atoms lose/gain electrons to have full outer shells - to become stable
What is an isotope?
(same atomic num but diff mass number)
- isotopes are different forms of the same element - that have same number of protons but different number of neutrons
ex: carbon - 12, carbon - 13
What is the relative atomic mass?
-different isotopes have diff masses, so we need to work out average mass of all isotopes that make up an element
How to work out relative atomic mass (Ar)?
sum of abundance of all isotopes
Example of relative atomic mass:
- copper has 2 stable isotopes:
1) copper - 63 (mass num) and abundance of 69.2%
2) copper - 65 (mass num) and abundance of 30.8%
so:
(69.2 x 63) + (30.8 x 65) divided by (69.2+30.8)
= Ar = 63.6169
What is the abundance in the relative atomic mass?
How common the isotope is
– its in a percentage that you need to multiply by the mass number of isotope
What is a molecule?
2 or more atoms held together by chemical bonds - can contain different elements
What is a compound?
2 or more DIFFERENT elements held together by chemical bonds - always found in fixed proportions + difficult to separate them (have to do chemical reactions)
- the properties of compounds are diff from properties of elements they’re from
Molecules and compounds?
- all compounds are molecules
- not all molecules are compounds
- molecules are just any 2 or more elements chemically combined
- compounds are two different elements chemically combined
What is a mixture?
- consists of 2 or more elements that are not chemically combined together - they haven’t reacted they’ve just been physically put together – to separate, need to use physical methods (filtration/crystallisation/distillation)
Metals form which ions?
- more on the periodic table (on left side)
- form positive ions (1+ ions)
Non metals form which ions?
- on right side of periodic table
- form negative ions (1- ions)
Physical properties of metals?
- very strong due to metallic bonds
- shiny
- malleable - can be bent without snapping
- good conductors of heat + electricity
- high melting and boiling point
- high density (weight)
Physical properties of non-metals?
- dull in colour
- brittle - break easily
- low boiling and melting point
low conductors of heat and electricity - lower density (weight)
Transition metals?
- in the middle of the periodic table
- have the same properties as metals
- can form more than 1 ion
- make good catalysts (speed up chemical reactions without being used up)
What are the columns on the periodic table called?
Groups
What are the rows on the periodic table called?
Periods
Are elements in the same group similar or different?
- may have similar chemical properties
- because they have same number of electrons on outer shells – group 2 have 2 electrons on outer shell/ group 1 has 1 electron
Who created the periodic table?
Mendeleev
What is similar about elements in same periods/rows?
- have same number of shells
The majority of elements in periodic table are?
Metals
Elements that react to form positive ions are?
Metals
Elements that react to form negative ions are?
Non-metals
