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3 years ago

What is the period number in which helium is found

Chemistry

2 answers:

julsineya [31]3 years ago

6 0

Answer:

Helium is the second element on the periodic table. It is located in period 1 and group 18 or 8A on the righthand side of the table. This group contains the noble gases, which are the most chemically inert elements on the periodic table. Each He atom has two protons and usually two neutrons and two electrons.

Explanation:

thoughtco.com

GaryK [48]3 years ago

5 0

Answer:

period 1 and group 18 or 8A on the righthand side of the table.

Explanation:

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3 years ago

The cylinder of aluminum in class was approximately 13mm in circumference and 42mm in length. What would be it's approximate mas

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Answer:

Mass, m = 1.51 grams

Explanation:

It is given that,

The circumference of Aluminium cylinder, C = 13 mm = 1.3 cm

Length of the cylinder, h = 4.2 cm

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Circumference, C = 2πr

$r=\dfrac{C}{2\pi}\\\\r=\dfrac{1.3}{2\pi}\\\\r=0.206\ cm$

Density is equal to mass per unit volume.

$d=\dfrac{m}{V}$

m is mass of the cylinder

V is the volume of the cylinder

$V=\pi r^2h\\\\V=\dfrac{22}{7}\times0.206^2\times 4.2\\\\V=0.5601\ cm^3$

So,

$m=d\times V\\\\m=2.7\times 0.5601\\\\m=1.51\ g$

So, the mass of the cylinder is 1.51 grams.

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4 years ago

Electron affinity is the measure of the attraction of an electron toward an isolated gaseous atom. When an electron is added to

zhuklara [117]

False

Explanation:

Electron affinity is negative when energy is absorbed and it is positive when energy is released.

Electron affinity is defined as the energy released in adding an electron to a neutral atom in the gas phase.

It is a measure of the readiness of an atom to gain an electron.

In a reaction where energy is released, electron affinity is usually positive. These reactions are called exothermic reactions.

Endothermic reactions in which energy is absorbed have negative electron affinity values.

Learn more:

Endothermic reactions brainly.com/question/12964401

#learnwithBrainly

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3 years ago