The Periodic Table (1.2) (M) Flashcards
What are the elements in the periodic table are arranged in order of? Why?
atomic (proton) number so that elements with similar properties are in columns, known as groups
What is in common between elements in the same group? What does this mean?
they have the same number of electrons in their outer shell (outer electrons) and this gives them similar chemical properties
In the periodic table, as you move down group 7, the boiling point increases. Why is this?
- the formula mass of atoms increase
- the intermolecular forces between the atoms become stronger
- more energy is needed to overcome these intermolecular forces
same for all non-elements (bar G8) as they often form diatomic molecules
Before the discovery of protons/neutrons/electrons, how did scientists attempt to classify elements?
by arranging them in order of their atomic weights
What is the problem with early periodic tables?
They were incomplete and some elements were placed in inappropriate groups (not matching properties) if the strict order of atomic weights was followed
How did Mendeleev overcome the problems with the early periodic table?
He left gaps for elements that he thought had not been discovered and in some places changed the order based on atomic weights
he only did 7 groups, leaving out the noble gases as they had not been discovered by 1869
2 points
Why was Mendeleev’s table considered accurate?
- Elements with properties predicted by Mendeleev were later discovered and filled the gaps.
- Knowledge of isotopes made it possible to explain why the order based on atomic weights was not always correct.
What ion do metals form?
positive
What are the elements tat do not form positive ions?
non-metals
The majority of elements are.. (metals or non-metals)
metals
Where are metals and non-metals found on the periodic table?
Metals are found to the left and towards the bottom of the periodic table.
Non-metals are found towards the right and top of the periodic table.
3 factors
The electrostatic forces of attraction depend on which factors
- distance between outermost electrons and nucleus
- the number of occupied inner shells (energy levels) which provide a shielding effect
- the size of the positive charge on the nucleus (called the nuclear charge)
What the elements in Group 0 of the periodic table are called?
the noble gases
What are the chemical properties of the noble gases? Why?
They are unreactive and do not easily form molecules because their atoms have stable arrangements of electrons (full outer shell)
2 needed
What are the physical properties of noble gases?
- low boiling point
- low density
How many electrons do noble gases have in their outer shell? What is the exception?
The noble gases have eight electrons in their outer shell, except for helium, which has only two electrons.
How does the boiling point of noble gases correspond with their position in the group?
The boiling points of the noble gases increase with increasing relative atomic mass (going down the group)
Where are the noble gases placed in the periodic table?
to the right of Group 7