How elements are arranged in the groups of periodic table

Chemistry

1 answer:

siniylev [52]3 years ago

7 0

Answer:

Explanation:

The chemical elements are arranged in order of increasing atomic number. The horizontal rows are called periods and the vertical columns are called groups. Elements in the same group have similar chemical properties. This is because they have the same number of outer electrons and the same valency.

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Write the appropriate symbol for each of the following isotopes: (a) Z 74, A 186; (b) Z 80, A 201; (c) Z 34, A 76; (d) Z 94, A 2

beks73 [17]

Answer: a) $_{74}^{186}\textrm{W}$

b) $_{80}^{201}\textrm{Hg}$

c) $_{34}^{76}\textrm{Se}$

d) $_{94}^{239}\textrm{Pu}$

Explanation:

General representation of an element is given as:_Z^A\textrm{X}

where,

Z represents Atomic number

A represents Mass number

X represents the symbol of an element

Mass number is defined as the sum of number of protons and neutrons that are present in an atom.

Mass number = Number of protons + Number of neutrons

In an atom, when neutrons or protons are lost or gains, it directly affects the mass number of an atom.

Atomic number is defined as the number of protons or number of electrons that are present in an atom.

It is characteristic of a particular element.

Atomic number = Number of electrons = Number of proton

a) Z 74, A 186: $_{74}^{186}\textrm{W}$

b) Z 80, A 201: $_{80}^{201}\textrm{Hg}$

c) Z 34, A 76: $_{34}^{76}\textrm{Se}$

d) Z 94, A 239.: $_{94}^{239}\textrm{Pu}$

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3 years ago

Which organism has a nerve net? A fish B hydra C flatworm D sponge

Kaylis [27]

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3 years ago

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A student is adding DI water to a volumetric flask to make a 50% solution. Unfortunately, he was not paying attention and filled

dalvyx [7]

Answer:

His results will be skewed because there was more water than stock solution. Which would cause the percentage solution to be less than 50% therefore the density would be less than the actual value.

Explanation:

The solution will have percentage less than that of 50%. Therefore the density would be less than the actual value.

Suppose there should be 50 mL of the solution, and he added 60 mL. So 10 mL of the solution is added more.

Suppose the mass of the solute is m.

Originally, the density is = $\frac{m}{50}$ $\left(\frac{\text{mass}}{\text{volume}}\right)$