Chemistry topic 1 Flashcards
What is an element
a pure substance made up of only one type of atom
What is a compound
2 or more elements chemically joined together
What is a mixture
2 or more elements or compounds that are not chemically joined together
What is a molecule
a group of atoms bonded together
State the chemical symbols-
Oxygen
Hydrogen
Helium
Calcium
Copper
Carbon
Iron
Potassium
Nitrogen
Sodium
O
H
He
Ca
Cu
C
Fe
K
N
Na
How are atoms formed?
They consist of a positively charged nucleus, containing protons and neutrons, surrounded by negatively charged electrons
What is a nucleus
dense, positively charged central part of an atom
What is the mass number
the total number of protons and neutrons found ON TOP of the symbol
what is the atomic number
the number of protons (which is equal to the number of electrons) found UNDER the symbol
what is standard form
shortened way of writing down very small or very big numbers. Formula-
a*10^n where a is always larger than 1 and smaller than 10
What is configuration
the arrangement of electrons in an atom
what does the group number tell you
how many electrons are in the outer shell of the atom. Elements in groups have similar chemical properties
How do you calculate the configuration
Find the atomic number which is the number of electrons. You are allowed 2 electrons in the 1st shell and 8 in the rest
What are ions
when atoms lose or gain electrons to achieve a full outer shell. They become stable but are no longer electrically neutral. Metal atoms lose electrons to form positive ions and non metal atoms gain electrons to form negative ions
why are atoms electrically neutral
Atoms are electrically neutral because they have equal numbers of protons (positively charged) and electrons (negatively charged).
What is a light microscope
light shines up through a specimen and through lenses where it bends to make an enlarged image
What are electron microscopes
they have greater magnification and resolution than light microscopes
why is a stain used
to make the organelles within a cell appear clearer
What is the resolution
the shortest distance between 2 points that can be seen as separate points
What are isotopes
atoms of the same element with different numbers of neutrons (different mass numbers)
what is relative atomic mass
the average value that takes account of the abundance of the isotopes of the element/average mass off all the isotopes that make up an element
formula-
(mass no. * abundance (%/100)) + (mass no. * abundance(%/100))
how are elements arranged in the periodic table
in groups and periods. Elements are arranged in order of increasing atomic number. elements with similar properties are in the same group
who created the periodic table
Mendeleev
what is stable?
an electronic configuration that has a full outer shell of electrons
What are the noble gases
-elements in group 0
-they have stable electronic configurations which means they are unreactive and do not easily form molecules
-inert (unreactive)
-the melting point increases as you move down the noble gases because the atoms get larger and more energy is needed to overcome these forces
what does inert mean
unreactive
what are the alkali metals
-elements in group 1
-1 electron in outer shell
-very reactive
-get more reactive as you move down the group because the outer electron is further away from the nucleus
-soft, shiny, low melting and boiling points
What are the halogens
-group 7
-similar chemical properties
-non-metals
-consist of diatomic molecules (2 atoms)
-as you move down the group the boilng and melting points increase because the molecules become larger and the forces between the, become stronger
-decrease in reactivity as you go down the group
sodium reacts with water
orange/yellow flame, fizzing
How can you prove that an alkaline solution is formed when sodium reacts with water?
universal indicator purple which is strongly alkaline
potassium reacts with water
pink flame, moves around surface
What numbers are acidic, neutral and alkaline on the pH chart?
ACIDIC-3-5
NEUTRAL-6-7
ALKALINE-7-11
formula for total magnification
magnification of eyepiece lens times magnification of objective lens
