C2 - Periodic Table Flashcards
How was the periodic table developed over time?
-elements used to be arranged by atomic mass
-Mendeleev left gaps for undiscovered elements, and switched the order of some elements, so that they would be placed in groups of elements with similar properties
-elements with properties predicted by Mendeleev were soon discovered, filling the empty gaps
Explain why early periodic tables were incorrect, and evidence that showed why:
-they were ordered by mass number, so some elements were grouped with others with completely different properties
-the knowledge of isotopes changed mass number and also changed their order
Why did Mendeleev’s periodic table become more widely accepted?
-Mendeleev had predicted the properties of missing elements
-these elements were later discovered and filled the gaps
-their properties matched Mendeleev’s predictions
Describe the elements found in group 0 and their properties:
-noble gases with full outer shells
-boiling point increases down the group
-unreactive, don’t form molecules easily (due to full stable outer shells) so they are just monatomic gases
They are not intermolecular forces as group 0 only forms monatomic gases
Describe the elements in group 1 and their properties:
-alkali metals with 1 outer electron
-reactivity increases down the group, while boiling point decreases
-reacts with water to form alkaline solution and hydrogen gas
Describe the elements found in group 7 and their properties:
-halogens, 7 outer electrons
-reactivity decreases down the group, while boiling point increases
-forms diatomic molecules
Remember they can make ionic compounds too, not just diatomic molecules
Generally, why might the boiling point of non-metals increase down a group? How would it be different if they were metals?
-increasing atomic radii
-as it is a non-metal, it is (usually) held together by weak IM forces
-stronger IM forces between molecules
-if they were metals, it would be the opposite as they form metallic bonds - the larger the atom, the weaker the force of attraction is between metal ions and delocalised electrons
What will a halogen do in a displacement reaction with another halogen?
the more reactive halogen will displace the less reactive halogen from a solution of the less reactive halogen’s salt
How are the properties of transition metals different to those in group 1?
Don’t give their unique properties for this card
(transition metals)
-higher melting/boiling points
-denser, stronger, and harder
-less reactive
Note that all metals have the property of being malleable/ductile, and good conductors of heat/electricity
What are some typical properties of transition metals that are unique in comparison to the alkali metals?
-forms coloured compounds (while group 1 forms white/colourless)
-used as catalysts
-can form ions with different charges
Generally, why might reactivity increase/decrease down a group?
-atomic radii increases
-weaker ES forces from the nucleus on outer electron(s) due to more inner electrons shielding them
-easier to lose outer electron, reactivity increases
OR
-harder to complete outer shell, reactivity decreases
Why is it not correct to the the boiling point of a bromine atom is 59°C?
-boiling point is a bulk property of a simple molecular substance
-it relates to the weak IM forces between diatomic bromine molecules, and not the strong covalent bonds inside the molecule
Gallium was discovered after Mendeleev’s periodic table was published - why did this help it to become accepted?
-it fit in a gap that he left
-its properties were correctly predicted and were similar to its group
Why might this reaction be carried out in an atmosphere of argon gas?
-argon is an inert gas (group 0)
-carrying it out in an atmosphere of normal air would cause the oxygen/water vapour to react with the sodium or the titanium produced
What is the difference between relative atomic mass and mass number?
-relative atomic mass is the average of all of an elements isotopes that accounts for their abundances
-mass number is just the sum of the number of protons and neutrons in a specific isotope
Atomic weight is an old way of saying relative atomic mass
