Atoms, Isotopes and the Periodic Table Flashcards
All substances are made of?
atoms
What is an atom?
An atom is the smallest part of an element that can exist
How many elements are there?
118
List all the “things” found in an atom
1) nucleus (protons and neutrons)
2) electrons
What is the nucleus?
It is a dense region in the middle of the atom composed of positive protons and neutral neutrons meaning it has a positive charge.
Almost the whole mass of the atom is concentrated in the nucleus
What are electrons?
They orbit the nucleus in fixed energy levels
They are negatively charged and tiny
Atoms have an overall charge of? and why?
0 - protons are positive and electrons are negative, and the number of protons and electrons in an atom are always equal.
What is an element?
A substance made up of atoms that all have the same number of protons in their nucleus.
What is an isotope?
Isotopes are different forms of the same element which have the same number of protons but a different number of neutrons
What is a compound?
A compound is a substance formed from 2+ elements whose atoms are all held together by chemical bonds, When elements react, atoms combine with other atoms to form compounds
What is a mixture?
A mixture consists of two or more elements or compounds not
chemically combined together. The chemical properties of each
substance in the mixture are unchanged.
Diagrams of Dalton, Thompson, Chadwick, Bohr and Rutherford’s models
https://www.guyhowto.com/atomic-models-explained/
Why was Dalton’s model discarded?
Thomson’s experiments with cathode ray tubes helped him to discover the electron. Dalton thought that atoms were indivisible particles, and Thomson’s discovery of the electron proved the existence of subatomic particles showing that atoms were not just empty spheres
Why was Thomson’s model discarded?
Rutherford’s gold foil experiment proved the existence of a nucleus inside the atom, which the plum pudding model didn’t have, leading to it being discarded
Why was Rutherford’s model discarded?
The main problem with Rutherford’s model was that he couldn’t explain why negatively charged electrons remain in orbit when they should instantly fall into the positively charged nucleus. This problem would be solved by Niels Bohr’s model leading to his being discarded
Given the mass number: x, and the atomic number: y, how many electrons, protons and neutrons are in atom z
protons = y electrons = y neutrons = x - y
What is an ion?
ions are charged particles due to the loss or gain of 1+ electrons
Why are ions formed?
Ions are formed because atoms try to lose or gain electrons so that they can have a full outer shell. Atoms with full outer shells are very stable.
When metals form ions they…
loose electrons from their outer shell to form positive ions
When non-metals form ions they…
gain electrons into their outer shell to form negative ions
Why do ions have charge?
The reason atoms don’t have charge is because protons are positive and electrons are negative, and the number of protons and electrons in an atom are always equal.
However, when atoms lose or gain electrons to try to have full outer shells, they no longer have equal numbers of protons and electrons and therefore will have an overall positive or negative charge
Electronic configuration and structure for sodium?
https://in.pinterest.com/pin/858709853943204204/
The periodic table is organised in…
ascending proton/atomic number
The group number is…
the number of electrons in the outer shell
what is the outer shell called
the valence shell
The period number is…
the number of shells
The table is called a periodic table because…
similar properties occur at regular intervals
Elements in the same periodic table group have…
the same number of electrons in their outer shell giving them similar chemical properties
Why are the electrons in the valence shell especially important?
Because they can engage in the sharing and exchange that is responsible for chemical reactions
Chadwick? Time?
1932
He proved the existence of neutrons and therefore the model we used today has neutrons and protons in the nucleus.
Why does chlorine not have a whole mass number?
The relative atomic mass of chlorine is 35.5 rather than a whole number. This is because chlorine has different isotopes
Relative atomic mass formula?
total mass of all atoms/total number of atoms
total mass = abundance * mass number for every isotope
total number of atoms = sum of abundances
