Periodic table and how the atom was formed
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Who made the plum pudding model
J J Thomson
When did Thomson discover his plum pudding model
1897
Explain Thomson’s plum pudding model
In 1897, an English physicist called J. J. Thomson discovered electrons. Thomson modelled the atom as a ‘plum pudding’ - a ball of positive charge (dough), with negatively charged electrons (currants in pudding) mixed in with the ‘dough’.
Who created the nuclear model
Ernest Rutherford
Explain the nuclear model
In 1909, Ernest Rutherford discovered that alpha particles could bounce back off atoms. Rutherford concluded that an atom’s mass is concentrated in the atom’s centre. This was called the “nucleus” and it contained positively charged particles called protons.
Who discovered the modern model
neil bohr
explain the modern model
Niels Bohr discovered that electrons orbit the nucleus at fixed distances.
what is an elements atomic number
the number of protons it has
where are protons found
in the nucleus
where are electrons found
in the fixed orbit around the nucleus
why do atoms have no overall charge
the total number of negative electrons equals the number of positive protons, meaning the charges cancel each other out
what is the relative mass of protons and neutrons
1
what is the relative mass of electrons
0.0005 which is rounded down to 0
how do you find the relative mass in atoms
number of protons+ the number of neutrons
how big are atoms
0.1 nanometres or 1x10 to the power of -10
compared to an atom, how big is the nucleus in an atom
10,000 times smaller
where is the mass number of an element found
at the top of the number
where is the atomic number found
at the bottom of the number
what is an isotope
an atom of the same element containing different number of neutrons
what is the relative atomic mass
the average mass of all of the isotopes of an element.
Who was the first scientist to devise a periodic table
John Newlands
How was Newlands table organised/ordered
by the mass (atomic weight) of elements
what was wrong with newlands table?
the table was incomplete and some elements were placed in inapropriate groups, elements in some groups did not react similarly with each other
Explain Dimitri Mendeleevs periodic table
• Dmitri Mendeleev recognised that there may be undiscovered elements. Mendeleev added gaps to Newlands’ table to account for undiscovered elements. • He also predicted the properties of these undiscovered elements and several years later, when these elements were discovered, their properties matched Mendeleev’s predictions • He also changed the order of elements based on their atomic weight • if he needed to, he would switch the order of specific elements, so that they fitted the patterns of other elements in that group