Unit 2 Periodic Table Flashcards
Dubereiner triads
Dobereiner Triads:
First scientist to organize the periodic table.
Arranged elements in groups of 3s called Triads.
Atoms in triads are in order of increasing atomic masses.
Triads have similar properties.
The atomic mass of a middle element in a triad is equal to the average A btw the other 2
Ex: Li, Na, K
(7+39)/2 = 23 = A of Na
Fails to arrange all elements in triads
John Newland’s Octaves
States that when elements are arranged in the order of their atomic mass the properties of the First and eighth elements will be similar.
Fails to arrange elements after Calcium. Didn’t work after Calcium
Assumed only 56 elements existed
Mendeleev’s periodic law
63 elements were discovered in his time.
He wrote the chem/phy properties of each element of n a card.
He made the element react with H and O because they are highly reactive and found everywhere
He arranged them in order of their atomic masses, he left places for elements that hadn’t discovered he believed to exist. And he predicted their properties almost perfectly.
Mendeleev’s periodic law: properties of elements are periodic functions to their increasing order of atomic masses.
This means that for every # of gaps the phy and chem properties will be similar
Modern periodic law
It was built based on Mendeleev’s periodic table. However, they changed the arrangement from increasing atomic mass to atomic number because it gave more accurate properties.
Modern Periodic Law / Periodicity: Properties of elements are periodic functions of their atomic number.
Define groups and periods
Groups: Elements are arranged in vertical columns which show similar chem properties.
Periods: Elements are arranged in horizontal rows showing different phy and chem properties.
Metals and non-metals properties
Metals: Hard, Ductile, Malleable, Conductor, Magnetic, Shiny.
Non-Metals: Brittle, not Ductile, not Malleable, Insulator, not Magnetic, Dull.
Ductility: The quality of being flexible.
Malleable: The quality of being shaped into something without breaking.
Dull: Lacking brightness.
Define Atomic Radius stating its trends.
Distance from outermost orbit to the nucleus. measuring an atom’s atomic radius in a bond form is easier
Covalent bond radius:
bond length(btw the 2 nucleus)/2
Atomic radius decreases as we move across a period (to the right) because the atomic number increases.
Atomic radius increases down a group because of the shielding effect.
Define Ionization Energy stating its trends
The energy required to remove 1 e- from the valence shell.
Lowest in gases then liquids the solids
Increases across a period because the Atomic number increases increasing the nuclear charge and decreasing the atomic radius.
Decreases down a group because the Atomic number increases increasing the nuclear charge but increasing the atomic radius because of the shielding effect.
Define Electronegativity stating its trends
The ability of an atom in a molecule to attract the shared pair of electrons toward itself.
Fluorine has the highest EN
Francium has the lowest EN of (0.7)
Across a period eN increases.
Down a group, eN decreases.
The size of an atom increases, EN decreases, and vice versa
Nuclear charge increases and electronegativity increases.
Group 1 elements, reason of naming, properties, where to store them.
Alkali metals. Alkali: Base
Li: least reactive
Na
K
Rb
Cs: most reactive
Fr: Radioactive
Called alkali metals because they form hydroxide with water and are alkaline in nature.
They are stored in oil or kerosene because they are reactive with O2 and moisture in the air.
They have low density.
Melting point and boiling point decrease down the group.
Softness and reactivity increase down the group
because as atomic size increases the strength of metallic bonds decreases.
Moreover, they have only 1 electron.
Reaction of Alkali metals with Water
They all Produce (metal) Hydroxide which is alkaline in nature and gives a purple color with a universal indicator.
Equation:
Word:
(metal)+water=(metal) Hydroxide+H2
Chem:
2(metal)+H2O=2MetalOH+H2
Lithium: moves quickly on the surface and floats because it has a lower density.
Bubbles of H2 go out with a pop sound. Reaction and melting are the slowest in this group.
Potassium: Melts into a shiny ball and moves around the surface. Forms bubbles of H2O with a pop sound.
React more vigorously than sodium.
Rubidium: explodes more vigorously than Na and K due to more production of heat and H2.
Cesium: Even more reactive
Francium: Too reactive
Alkaline Earth metals, Halogens, and Transition metals properties
Alkaline Earth Metals:
1)Group 2 elements that have 2 valence e-.
2)Highly reactive (less than group 1)
3) Good conductors with moderate density.
4) High boiling and melting points.
Halogens:
1)Group 7 elements that have 7 valence e-.
2)Dio atomic molecules (exist naturally as pairs)
3)Poor conductors with Low Melting and Boiling Points.
4) Highly reactive.
Transition metals:
1) Groups 3 to 12.
2) High Melting and Boiling Points.
3) Hard with High Densities.
4) Good conductors and used as catalysts
Noble gases and metalloids properties.
Noble gases:
1) Group 18 with full outer shell (8 e-).
2) Low Melting and Boiling Points.
3) Unreactive/Stable.
4) Colorless with low density.
Metalloids:
1) Found in groups 13, 14, 15, and 16.
2) Weak conductors compared to metals.
Deducing Formula in Ionic compounds
Balancing subscripts in a compound formula.
Magnesium bromide:
Mg: Group 2, Bromine: Group Group7
We use cross-multiplication:
Mg: 2 (needs to lose 2 for stability)
Br: 1 (needs to gain 1 for stability)
ANS: MgBr2
Calcium nitrate:
Calcium= Group 2, Nitrogen= Group 5
we use cross-multiplication:
Ca = 2 (needs to lose 2 for stability)
NO3 = 1 (needs to gain 1 for stability)
ANS: Ca(NO3)2
