Atoms Flashcards
define - atom
basic building blocks of matter
define - nucleus
organelle inside cell - contains DNA
electon shells
outside part of an atom around the atomic nucleus
atomic number
number of protons an atom has
Protons - charge and location in atom
positive charge
located in nucleus
mass number
number of protons + neutrons
describe structure of an atom
- Each atom is made up of smaller particles - electrons,protons & neutrons (subatomic particles).
- the center of the atom is the nucleus.
- Nucleus constraints protons and neutrons.
neutrons - charge and location in atom
neutral charge
located in nuclues
electrons - charge and location in atom
negative charge
located outside the nucleus in the electron shells
what is meant by a neutral atom
number of protons is equal to number of electrons
atom in neutral
Electron shells and arrangement
- electrons are arranged in shells (energy levels)
- the levels CLOSEST to the nucleus are of LESS energy
- Electron cloud model (or wave model)
- spherical cloud of varying density
- varying dentistry shows where an electron is more or less likely to be
Maximum number of electrons in each shell.
2,8,8,2 ( first 20 elements)
RULE : 2n^2 - (n = shell number)
Relate the number of valence electrons to the group number on the periodic table
periods (horizontal) = number of shells that contain electrons
groups (vertical) = number of electrons in valence shell.
- for groups 13-18, subtract 10
Flame tests and the colours of metal ion
- heating an element can cause an electron to absorb energy & jump to a higher energy level or shell
electron is excited & unstable & quickly returns to a lower energy level, releasing a fixed amount of energy which may be in the form of coloured light
VISIBLE LIGHT can be emitted when electrons return to a lower energy level.
Explain why the outer shell (valence shell) electrons are important
valence shells are important because they determine an atom’s chemical properties & ability to bond with other atoms.
ion
an atom that carries positive or negative electric charge as a result of having lost or gained electron/s.
cation
a positively charged ion formed by losing electrons
Why do atoms form ions?
atoms form ions to achieve a stable electron configuration. by gaining or losing electrons to attain a full outer shell.
anion
a negatively charged ion formed by gaining electrons
which type of element form anions
non-metals
which type of metals form ions
metals
Explain the difference between cations and anions.
Cations are positively charged ions formed by losing electrons
anions are negatively charged ions formed by gaining electrons.
Explain how bonds form between ions
when a metal cation and a non-metal anion react together in a chemical reaction an ionic bond is formed.
List the experimental observations indicating that a chemical reaction has occurred
COBALT
C- colour changed
O-odor change
B-bubbles appearing
A- Appearance or disappearance of a solid
L-Light or sound produced
T- Temperature change
What are the reactants of a chemical reaction?
the subatances you have at the beginning are called reactants.
What are the products of a chemical reaction?
when the reaction is complete, you have new substances which are called the products.
Describe the difference between a physical and a chemical change.
- a physical change involves change in physical state or appearance without altering its chemical composition. (shape,size)
chemical change involves the formation of new substances with different chemical properties.
List the factors that can increase the rate of a chemical reaction
anything that increases the number of successful collisions between reactant particles will speed up a reaction
- increased temperature
- increased concentration of dissolved reactants
- increased surface area of solid reactants
- use of a catalyst.
Explain the meaning of ‘rate of a chemical reaction’
The rate is a measure of how fast the products are made or reactants are used up.
The speed of a reaction is called the rate of the reaction.
Explain how these factors increase the reaction rate
higher temp
- At a higher temperature, particles have more energy. This means they move faster and are more likely to collide with other particles.
- When the particles collide, they do so with more energy, and so the number of successful collisions increases.
Explain how these factors increase the reaction rate
- catalyst
a catalyst speeds up a chemical reaction. a catalyst provides a surface for the reactions to take place on and hence increases the frequency of collins.
It also provides a different pathway for the ration with lower energy required.
Explain how these factors increase the reaction rate
higher concentration
at a higher concentration there are more particles in the same amount of space. This means that the particles are more likely to collide and therefore more likely to react.
explain the function of a catlayst
A catalyst speeds up chemical reactions by lowering the energy needed to start them, making reactions happen faster. It does this without being used up itself.
