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Model of matter- Atoms and molecules - Coggle Diagram
Model of matter- Atoms and molecules
What is the simplest unit of an element and how do we represent its structure
elements consists of atoms
atoms are so small that they cannot be seen with the naked eye
Some comparisons include
A row of 50 million hydrogen atoms can take up the length of a grain of rice that is about 0.5 cm
A row of 100 million hydrogen atoms can take up the length of a fingernail that is about 1 cm
A row of 1 million carbon atoms can take up the diameter of a strand of human hair that is between 0.001 cm to 0.006 cm
Structure of an atom
An atom contains three types of sub-atomic particles
neutron
A neutron is a particle with no charge
electron
An electron is a negatively charged particle. it moves around the nucleus at high speeds
proton
together they form the nucleus of an atom
The nucleus is made up of neutrons and protons. Thus it is positively charged
/.-./
A proton is a positively charged particle
The atom was first imagined to be like a hard billiard ball. This is known as the billiard ball model. It was introduced by a scientist called John dalton.
A later model imagined the atom to be like a plum pudding such that electrons (plums) were found within the mass of protons (pudding) The model was created by a scientist called J.J Thomson in the early 1900s
Both of these models are now considered inaccurate because they are not able to explain many properties of atoms
Charge of an atom
Protons
Relative charge of +1
Relative mass of 1
Within the nucleus
Neutron
Relative charge of 0
Relative mass of 1
Within the nuxcleus
Electron
Relative charge of -1
relative mass of 1/1840
Around the nucleus
Number of protons is equal to the number of electrons. Thus, the positive and negative charges in the atom are balanced.
how can the number of protons in an atom be used to identify an element?
The number above the chemical symbol of an element in the periodic table is known as the proton number
This is the number of protons in an atom of an element.
for example, the proton number of helium is 2. This means that a helium atom contains two protons
elements are arranged in the periodic table in order of increasing number of protons in their atoms.
no two elements can have the same number of protons in their atoms.
the number of protons in atoms differentiates one element from another
elements are different from one another as they have unique atomic structures
number of sub-atomic particles in hydrogen, helium and lithium atoms
hydrogen
proton----->1
electron---->1
neutron------>0
helium
proton---->2
electron---->2
neutron---->2
lithium
proton------>3
electron----->3
neutron----->4
number of neutrons in a atom
nitrogen atom
number of protons-7
number of electrons-7
number of neutrons-7 or 8
Unlike the number of electrons, the number of neutron in an atom is not always equal to the number of protons in the atom. Some atoms have different numbers of neutrons
uranium atom
number of protons-92
number of electrons-92
number of neutrons- 143 or 146
carbon atom
number of protons-6
number of electrons-6
number of neutrons-6,7 or 8
The mass of an atom is mainly contributed by the mass of it's nucleus or the mass of protons and neutrons in the nucleus. Electrons have mass, but they are very much lighter compared to protons and neutrons. Thus, the mass of the electrons in an atom is considered negligible and does not add up to the mass of the atom
An atom can combine with one or more atoms of the same element or different elements to form molecules. A molecule is made up of two or more atoms that are chemically combined
For example, a hydrogen molecule is made up of two hydrogen atoms. Thus, it can be represented by two circles that are labelled with H and joined together. The total number of atoms in one hydrogen molecule is two.
to represent an atom of an element, a single circle labelled with the chemical symbol of the element is used.
For example, a hydrogen molecule is made up of two hydrogen atoms. Thus, it can be represented by two circles labelled with H, and one other circle labelled with O, which are joined together. The total number of atoms in one water molecule is 3
Chemical formula
is another way to represent molecules
it identifies each constituent element in a molecule by its chemical symbol and indicates the number of atoms of the element
what the chemical formulae of hydrogen and water denote
hydrogen
chemical formula--> H2
type of atom in the molecule-->hydrogen
number of atoms in the molecule-->2
water
chemical formula-->H2O
type of atom in the molecule---> hydrogen and oxygen
number of atoms in the molecule hydrogen--->2
oxygen----> 1
A molecule of an element consists of only one type of atoms that are chemically combined. Examples are nitrogen (N2) and oxygen (O2)
A molecule of a compound consists of two or more type of atoms that are chemically combined. An example is nitrogen (N2) and oxygen (O2).
some elements and compounds represented by their chemical formulae
element----> oxygen
chemical formula---> O2
compound--->ammonia
chemical formula----->NH3
element----> nitrogen
chemical formula----->N2
compound---->carbon monoxide
chemical formula---->CO
element ---> hydrogen
chemical formula--> H2
compound----> water
Chemical formula------>H2O
element---->chlorine
Chemical formula---->Cl2
compound----->carbon dioxide
chemical formula----->CO2
element---->iodine
chemical formula------>l2
compound------> hydrogen chloride
chemical formula------>HCl
What are some applications of atomic technologies and the possible issues that can arise from them
The knowledge of atoms has been used for medical purposes and to provide nuclear energy
The properties of atoms are applied in radiation therapy to cure diseases
as well as in medical imaging
Which includes magnetic resonance imaging (MRI) and X-ray
Energy from atoms is used in nuclear power plants and atomic bombs
Accidents at nuclear power plants can result in the loss of lives and environmental pollution, While the use of atomic bombs can bring about destructive effects
social and ethical issues often arise from scientific discoveries. Resolving theses issues requires a good understanding of scientific applications and sound moral values from everyone . We need to actively understand and debate these issues in order to make wise decisions that benefit mankind
For example, gold plated orchids exist in Singapore today because a local biochemist managed to coat living plant material with gold atoms
overall charges of some atoms
helium
protons---->2
electron----->2
overall charge----->0
lithium
protons---->3
electron----->3
overall charge----->0
hydrogen
protons----->1
electron---->1
overall charge---->0
