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3 years ago

How to find the valence electrons on a periodic table + energy levels?

1 answer:

3 0

The answer is elements in the first row (hydrogen and helium) will have outer electrons in the first energy level. Their principal quantum number is 1. Elements in the second row (lithium through neon) will have valence electrons in the second energy level with a principal quantum number of 2. I hope that helps.

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The half-life for the radioactive decay of calcium-47 is 4.5 days. how many half-lives have elapsed after 27 days?

Evgesh-ka [11]

1 half-life - 4.5 days
x half-lives - 27 days

x=(1*27)/4.5=6
6 <span>half-lives have elapsed after 27 days.</span>

8 0

4 years ago

Read 2 more answers

The subshell letter:a) specifies the 3-D shape of the orbital.b) specifies the principal shell of the orbital.c) specifies the p

Dafna11 [192]

Answer:

a) specifies the 3-D shape of the orbital

Explanation:

To determine the region where is more probable to find the electron, it is characterized by four quantum numbers:

- Principal quantum number (n): represents the level, or shell, where the electron is. It varies from 1 to 7, and are represented by the letters K, L, M, N, O, P, and Q.

-Azimuthal quantum number (l): represents the sublevel, or subshell. Is represented by the letters s, p, d, f, g, ... And by the numbers 0, 1, 2, 3, ... Each one has a 3-D shape, the s, for example, has a spherical shape.

-Magnetic quantum number (ml): represents the orbital inside the subshell, and varies from -l to +l, passing by the 0. Each orbital can have at least 2 electrons.

-Spin quantum number (ms): represents the spin of the electron, which can be +1/2 or -1/2.

3 0

3 years ago

Chemists can use moles to calculate: A. How much of the products are needed and how much reactant will be made. B. How much prod

damaskus [11]

Answer:

c.- How much of the reactants are needed and how much product will made.

Explanation:

The moles is the matter unit used in chemistry to simplify some calculations, instead of using grams. Also the moles are very useful because the chemical reaction can be balanced.

When a Chemical reaction is balanced, then it can be easily to calculate how many moles are necessary to add in a process to obtain a quantity of grams of a product.

5 0

3 years ago

What is the total mass of solute in 1000. grams of a solution having a concentration of 5 parts per million?

Art [367]

50 grams or 50,000 mili grams is the mass of solute in 1000 grams of a solution having a concentration of 5 parts per million.

Explanation:

Total mass of solution = 1000 grams or 1000 ml since 1 gram = 1 ml

concentration is 5 parts per million ( 5 mg in 1000 ml solution or 0.005 gram in 1000 ml)

the formula used for parts per million:

parts per million = $\frac{mass of solute (mg)}{volume of solution}$

putting the values in the equation:

parts per million = $\frac{mass of solute}{volume of solvent}$

0.005 x 1000 = mass of solute

50 grams= mass of solute

converting this into mg

50,000 mg. is the total mass of solute in 5ppm of 1000 ml solution.

4 0

3 years ago

The natural tendence of an object to resist change in its state of motion is:

melisa1 [442]

Inertia. Inertia is the natural tendency of bodies to remain in their states of either rectilinear or resting motion.

5 0

3 years ago