t1-periodic table Flashcards
what was an early attempt to classify elements
arranging them in order of atomic weight (relative atomic mass)
what 2 things were wrong with the early attempt of classifying elements
they were incomplete because many elements were unknown
some elements were placed in groups with elements that were not similar to them
how did mendeleev order elements
in order of increasing atomic weight
he took into account the properties of the elements and their compounds
what 2 things did mendeleev’s table have
gaps
elements with similar chemical properties lined up in groups
Why did Mendeleev’s periodic table become more widely accepted than previous versions
-he predicted properties of missing elements
-elements were discovered (that
filled the spaces / gaps)
-the properties of these elements
matched Mendeleev’s predictions
describe the trend in reactivity in alkali metals
increase down the group
-outer electron+nucleus get further away so there’s a weaker force of attraction so the outer electron is lost more easily
properties of alkali metals
soft
low mp- decreases down the group
low density
alkali reaction with non metals
-form ionic compounds
-white solids formed
-dissolve in water to form colourless solutions
alkali reaction with water
-react vigorously
-forms metal hydroxide and hydrogen gas
-from potassium onwards, it ignites
alkali reaction with chlorine gas
form white metal chloride salts
alkali reaction with oxygen
form metal oxides
trends of halogens
-mp+bp increase down the group
-reactivity decreases sown the group
why does reactivity of halogens decrease down the group
outer electron is further from nucleus so theres a weaker force of attraction used to gain an electron
halogen reaction with metals
-form ionic bonds
-when a halogen gains an electron it becomes a halide
displacement reaction colours
-halide salts- colourless
-bromine water- orange
-chlorine water- colourless
-iodine water- brown
