18) Define periodic law or periodicity. ANSWER ON ATTACHED SHEETS 19) What is th

Question

18) Define periodic law or periodicity. ANSWER ON ATTACHED SHEETS 19) What is the mass, in grams, of a single atom of the element that is named for the founder of the modem periodic table? YOU MUST SHOW YOUR WORK ON ATTACHED SHEETS PLACE ANSWER HERE _________________________ 20-21) Write the name and the symbol for the metalloid in the fifth period having six valence electrons. 20) PLACE NAME HERE __________________________ 21) PLACE SYMBOL HERE 22) How many elements are gasses at room temperature and pressure? PLACE ANSWER HERE ________________ 23) How many valence electrons are in an atom of the element found in the fourth period in group IVA? PLACE ANSWER HERE

Explanation / Answer

18)

periodicity: property of elements in which chemical/physical properties ten to "repeat" in periods i.e. 8 elemtns or so

19)

mass in grams of 1 atom of the founder of modern periodict table...

The founde irs mendelev... its element is mendelevium Md

MW = 258 amu

1 mol = 258 g/mol

1 mol = 6.022*10^23 atoms

mass of 1 atom = 258 g/mol / 6.022*10^23 atoms/mol = 4.284*10^-23 grams

20-21)

Metaloid of the fifht period, with 6 electron valence

there are 2 metalloids in the 5th group :Sb and Te

The 6 electron valence must be Tellerium

23)

The group IVA, its the carbon group/familiy, they have 4 electron in its valnce shell

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