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3 years ago

Scientists use _____ as chemical symbols.

2 answers:

7 0

The periodic table, which consists of 109 elements, that we know of, it was existing still before we got the systematic method. Jons Jacob Berzelius assigned these elements in place. The symbols always consist of 1 or 2 letters, first one is capital, and the 2nd one, (if its there) is always lowercase.

Short Answer: Periodic Table

Hope i helped.

love history [14]3 years ago

6 0

A single element on the periodic table

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What is the energy per photon absorbed during the transition from n = 2 to n = 3 in the hydrogen atom?

adelina 88 [10]

Answer : The energy of one photon of hydrogen atom is, $3.03\times 10^{-19}J$

Explanation :

First we have to calculate the wavelength of hydrogen atom.

Using Rydberg's Equation:

$\frac{1}{\lambda}=R_H\left(\frac{1}{n_i^2}-\frac{1}{n_f^2} \right )$

Where,

$\lambda$ = Wavelength of radiation

$R_H$ = Rydberg's Constant = 10973731.6 m⁻¹

$n_f$ = Higher energy level = 3

$n_i$ = Lower energy level = 2

Putting the values, in above equation, we get:

$\frac{1}{\lambda}=(10973731.6)\left(\frac{1}{2^2}-\frac{1}{3^2} \right )$

$\lambda=6.56\times 10^{-7}m$

Now we have to calculate the energy.

$E=\frac{hc}{\lambda}$

where,

h = Planck's constant = $6.626\times 10^{-34}Js$

c = speed of light = $3\times 10^8m/s$

$\lambda$ = wavelength = $6.56\times 10^{-7}m$

Putting the values, in this formula, we get:

$E=\frac{(6.626\times 10^{-34}Js)\times (3\times 10^8m/s)}{6.56\times 10^{-7}m}$

$E=3.03\times 10^{-19}J$

Therefore, the energy of one photon of hydrogen atom is, $3.03\times 10^{-19}J$

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3 years ago

Suppose a man pushes a crate with a force of 20 N north. What is the magnitude and direction of the reaction force?

Goryan [66]

20 N north because He is pushing it 20 newtons north.

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3 years ago

Julli [10]

Answer: C. Metals are found on the left side of the periodic table.

Explanation:

The periodic table contains vertical columns called as groups and horizontal rows called as periods.

Period 2 contains 8 elements which are lithium, beryllium , boron , carbon, nitrogen, oxygen , fluorine and neon. Only Lithium and beryllium are metals.

Group 18 contains all the noble gases which are all non metals.

Metals are the elements which loose electrons easily and form positive ions. Non-metals are the elements which can gain electrons easily and form negative ions.

Metals are present on left side of the periodic table and as we move to right side of the periodic table , the metallic character decreases and thus non metals are found on the right side of the periodic table.

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3 years ago

The friction that prevents an object from moving when a force is applied is ________ friction.

uranmaximum [27]

Static friction is what you are looking for.
Kinetic friction is the force exerted on an already moving object, slowing it down.

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