The number of electrons in an element with atomic number 20 is

8 answers
Question:

The number of electrons in an element with atomic number 20 is

Answers

the answer is calcium

The number of electrons in an element with atomic number 20 is calcium

1 A
2 D
3 D
4 B
5 D
6 C
7 C
8 A
9 A
10 B

1. Mendeleev's periodic table of elements was organized by,

             Mass

Explanation:

                       Mendeleev was a Russian chemist who worked on periodic table after John Newland. Mandeleev arranged the elements in periodic table in order of their relative atomic masses. It was realized by Mendeleeve that most of the chemical and physical properties of elements were related to their atomic masses. Also, these properties were found to repeat after a specific periodicity hence, he arranged the elements with same properties in a vertical columns now known as groups.

2. Compared with Group 6A elements, Group 2A elements have,

               Fewer valence electrons.

Explanation:

                       Group 6A also known as oxygen family has a general valence shell electronic configuration as shown below,

                                                      ns², np⁴

                       While, Group 2A also known as Alkaline earth metals have a general valence shell electronic configuration as shown below,

                                                      ns²

Therefore, it is concluded that the Group 2A elements have 2 valence electrons while, 6A elements have 6 valence electrons in valence shell respectively.

3. Which element is found in most of the compounds in your body except for water?

               Carbon

Explanation:

                     Our body contains organic compounds. Organic compounds are those compounds which are made up of carbon atoms. Due to peculiar behavior of Carbon it has a property of Catenation (self linkage), isomerism (compounds having same molecular formula but different structural formula) and multiple bond formation (single, double and triple bonds) it results in the formation of numerous organic compounds in our body including proteins, enzymes, lipids, and much more.

4. Which of the following Group 1A elements is the least reactive?

               Lithium

Explanation:

                     Reaction rate of Group 1A depends upon the ionization energy of particular element. Smaller the ionization energy greater is the reactivity of that element. Hence, Lithium having the greatest ionization energy will be the least reactive and Cesium having the least ionization energy will be the most reactive element.

5. To keep them from reacting, some highly reactive elements are stored in,

               Argon

Explanation:

                         In order to keep them away from reacting one should keep the compounds in inert environment. In given Argon is the substance which belongs to Group of inert class of elements called as noble gases. Noble gases are least reactive because they have their valence shell complete. Hence, with complete octet noble gases are the stable elements hence least reactive.

6. The tendency of an element to react is closely related to

               The number of valence electrons in atoms of the element.

Explanation:

                     Atoms react with each other to form a molecule or compounds in order to gain stability. For example,

                                        2 Na  +  Cl₂    →    2 NaCl

In above reaction sodium metal losses one electron and chlorine gains one electron. Also, sodium only looses one electron because it has only one valence electron so by loosing that electron it gains a stable electronic configuration of Neon. On the other hand Chlorine has 7 valence electrons so in order to gain a noble gas configuration of Argon Cl gains one electron. Hence, we can conclude that the valence electrons are responsible for the reactivity of elements.

7. The usefulness of Mendeleev’s periodic table was confirmed by

               The discovery of elements with predicted properties.  

Explanation:

                      As discussed earlier Mendeleev arranged elements with same chemical properties in a vertical columns called as groups. At that time few elements were still not discovered hence their position was reserved in advanced and their properties were predicted bases on the properties of elements present in the same groups.

8. Group 8A of the periodic table contains the

               Least reactive nonmetals.  

Explanation:

                          Already discussed, Group 8 elements also called as noble gases are inert in nature and are least reactive in nature. The reason for least reactive nature is the complete octet. As atoms have reactivities due to loosing or gaining electron in order to gain noble gas configuration, Noble gases don't follow that trend as it already has a complete octet.


Remaining Questions are attached below.

Explanation:

1.Which elements had complete outer shells? Give the name and symbol for each

The elements with outer complete shells are the noble gases or inert gases or Group O elements. They are said to have a completer octet.

The elements in this group are:

Helium     He Neon          NeArgon          ArKrypton       KrXenon         Xe Radon          Rn

2. What do you notice about the location of the elements in #1?

The elements here are located in the last group on the periodic table and it is the p-block.

3. Which elements had only one valence electron?

The alkali metals have only one electron in their outermost shell. They are located in the first group on the periodic table. This group is made up of metals.

4. What do you notice about the location of the elements in #3?

They are located in the first group on the periodic table and they have one valence electron

5. What do you notice about the number of valence electrons as you move from left to right across a  row or period in the periodic table? (Na - Mg - Al Si P S - CI - An

The number of valence electrons increases from left to right on the periodic table. Moving across a period is like going from one group to another and the number of valence electrons increases in that manner.

6. What do you notice about the number of energy levels or shells as you move down a group or  column in the periodic table? (H Li - Na)

The energy levels increases. As one goes down a group the atomic radii increases as new energy levels and electronic shells are added to corresponding atoms.

7. Elements are organized into families according to their physical and chemical properties. Identify the  elements that you used in Step 5 that belong to each family based on the number of valence  electrons. Give the name and symbol for each element,

  Group 1 or family 1 elements:

                Lithium           Li

                Sodium          Na

                Potassium       K

                Rubidium        Rb

                 Cesium          Cs

                Francium         Fr

All of the elements in this group have similar chemical and physical properties. They all have one electron in their valence shell.

Alkali Metals - 1 valence electron

Alkaline Earth Metals - 2 valence electrons

Boron Family - 3 valence electrons

Carbon Family 4 valence electrons

Nitrogen Family - 5 valence electrons

Oxygen Family - 6 valence electrons

Halides - 7 valence electrons

Noble Gases - Complete outermost shell

8. What do you notice about the location of the elements in each family?

The location of each element in the family is based on the atomic numbers. This is the number of protons an atom contains.

Each element is arranged in vertical columns and they all have the same number of valence electrons.

9. How would you classify hydrogen? Why?

I will classify hydrogen as a Group O element.

Hydrogen has just one electron. This electron is located in the 1s orbital and half-filled orbitals are also stable like fully filled orbitals.

Also, hydrogen is a gas and it cannot be put into a group of metals. Therefore it would fit well into the noble gases.

10. Predict the number of valence electrons for each element based on its location in the Periodic Table  of Elements. You will need to use the table in your textbook

Barium                2 electrons                    Alkali earth metals

Xenon                 8 electrons                   Noble gases

Potassium          1 electron                       Alkali metals

Learn more:

Periodic table

Alkali metals

#learnwithBrainly

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THE ANSWER IS A C

Explanation:

I don’t know the answer but I know you’re attractive

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