SC3 & SC4 Flashcards
What are atoms made up of?
Protons, neutrons and electrons
What are electrons?
They move around the nucleus in electron shells
Negatively charged
Mass nearly nothing
Atom mostly empty space
What does the nucleus (in the middle of an atom) contain?
Protons and neutrons
The nucleus contains nearly all the mass of an atom
What are protons?
Positively charged
Has a relative mass of 1
What are neutrons?
They have a neutral charge
Has a relative mass of 1
What was the original order for elements in the periodic table?
They were originally placed in order of the masses of their atom
What is the order for elements in the periodic table now?
The modern periodic table places the elements in order of the number of protons in the atom
What is the atomic number?
The number of protons in an atom
All the atoms in a particular element have the same unique atomic number
What is the mass number(atomic mass)?
The number of protons + neutrons
How do you work out the number of electrons in an atom?
The number of electrons always equal the number of protons
This is why atoms are neutral
How is the charge of protons and electrons related?
They’re both the same size but opposite (protons positive, electrons negative)
What happens to the charge in ions?
In an ion, the number of protons don’t equal the number of electrons
E.g. an ion with 2- charge = 2 more electrons than protons
What is an isotope?
An isotope is a version of an element with different numbers of neutrons
They have the same atomic number but different mass number
What is relative atomic mass?
It is the average mass of all that element, compared to carbon having a mass of -12
Why is the RAM of helium if it’s mass is -4?
The RAM would be 4 as its 1/3 of carbon (-12)
How do you calculate RAM?
RAM= total number of atoms/the number of atoms
How did Mendeleev organise the periodic table?
He rearrange these elements in order of increasing relative atomic masses but left gaps in his table as he not always keep to this order
How did his assumption that new elements would continue to be discovered, help him to place existing ones?
Vertical columns= elements with increasing relative atomic mass
Horizontal rows= elements with similar chemical properties
What did Moseley discover after he showed that it was an elements physical property that gave its position in the periodic table?
For every increase in tonic number, there was a step in change in the energy of those X-Rays
Realised atomic number=number of positive charges in the nucleus
How are elements arranged in the modern periodic table?
Elements in row or period are in order of increasing atomic number
Elements with similar properties are in same column or group
Non metals are on the right of the table
What is the maximum number each shell can hold?
The first shell can contain up to 2 electrons
The second and third shell can contain up to 8 electrons
How are electron configurations and the periodic table related?
The number of occupied shells is equal to the period number
The number of shells in the outer shell is equal to the group number
