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3 years ago

Look up the word periodic in the dictionary propose a reason for the naming of the periodic table

Chemistry

1 answer:

kompoz [17]3 years ago

3 0

Meaning of Periodic in dictionary was found to be "<em>appearing or occurring at intervals</em>".

Purpose of Reason for naming the Periodic Table:

The elements is periodic table have been found of having same iso-electronic properties and the major periodicities found are of two, eight and eighteen respectively.

Examples:

First Group elements tends to loose only one electron to form M⁺ cation. Starting from Lithium with atomic number 3, secondly sodium which has atomic number 11. When 3 (lithium) is subtracted from 11 (sodium) (i.e. 11-3=8) eight is attained. Same when 11 (sodium) is subtracted from 19 (Potassium), again 8 is obtained. Going downwards the group the number of 18 is obtained i.e. Rubidium (37-19=18), Cesium (55-37=18).

Seventh Group elements tends to gain only one electron to form X⁻ anion. Starting from Fluorine with atomic number 9, secondly Chlorine which has atomic number 17. When 9 (Fluorine) is subtracted from 17 (Chlorine) (i.e. 17-9=8) eight is attained. Same when 17 (Chlorine) is subtracted from 35 (Bromine), 18 is obtained. Going downwards the group the number of 18 is obtained i.e. Iodine (53-35=18).

<h3>Conclusion:</h3>

Hence, we can conclude that Periodic Table is designed in such a way that after a particular interval the chemical and physical properties of elements repeats. Therefore, it can help in understanding the nature of elements without going into experimental experiments.

You might be interested in

what criteria are likely to dictate certain pairs of elements to undergo ionic bonding and others covalent bonding?

Paha777 [63]

Answer:

If one element is a metal and the other element is a non metal

Explanation:

Ionic bonds are formed between metals and non metals. The nonmetal atom receives electron(s) from a metal atom to form an ionic substance. This means that ionic substances are basically an ion pair.

Covalent bonds are mostly formed between two nonmetals. These elements share electrons with each other in order to form the compound.

7 0

3 years ago

For the main group elements( excluding the transition elements) , is it necessary to memorize the type of ion each element makes

vagabundo [1.1K]

Yes, you should memorize them. While it is easy to predict them by looking at a periodic table, you should still have a strong grasp of simpler chemistry such as this before more challenging topics are taught.

3 0

3 years ago

Under certain conditions, the substance ammonium chloride can be broken down to form ammonia and hydrogen chloride. If 29.4 gram

lina2011 [118]

Answer: 20.0 g of hydrogen chloride must simultaneously be formed

Explanation:

The balanced chemical reaction is :

$NH_4Cl\rightarrow NH_3+HCl$

According to the law of conservation of mass, mass can neither be created nor be destroyed. The mass on reactant side must be equal to the mass on product side.

Thus mass of reactants = mass of products

Given : mass of ammonium chloride = mass of reactants = 29.4 g

mass of ammonia = 9.4 g

mass of products = mass of ammonia + mass of hydrogen chloride

9.4 g +mass of hydrogen chloride = 29.4 g

mass of hydrogen chloride = 20.0 g

5 0

3 years ago

Excess magnesium reacts with 165.0 grams of hydrochloric acid in a single displacement reaction.

JulsSmile [24]

Answer:

The volume of hydrogen gas produced will be approximately 50.7 liters under STP.

Explanation:

Relative atomic mass data from a modern periodic table:

H: 1.008;
Cl: 35.45.

Magnesium is a reactive metal. It reacts with hydrochloric acid to produce

Hydrogen gas $\rm H_2$ , and
Magnesium chloride, which is a salt.

The chemical equation will be something like

$\rm ?\;Mg\;(s) + ?\;HCl \;(aq)\to ?\;H_2 \;(g)+ [\text{Formula of the Salt}]$ ,

where the coefficients and the formula of the salt are to be found.

To determine the number of moles of $\rm H_2$ that will be produced, first find the formula of the salt, magnesium chloride.

Magnesium is a group 2 metal. The oxidation state of magnesium in compounds tends to be +2.

On the other hand, the charge on each chloride ion is -1. Each magnesium ion needs to pair up with two chloride ions for the charge to balance in the salt, magnesium chloride. The formula for the salt will be $\rm MgCl_2$ .

$\rm ?\;Mg\;(s) + ?\;HCl\;(aq) \to ?\;H_2 \;(g)+ ?\;MgCl_2\;(aq)$ .

Balance the equation. $\rm MgCl_2$ contains the largest number of atoms among all species in this reaction. Start by setting its coefficient to 1.

$\rm ?\;Mg\;(s) + ?\;HCl\;(aq) \to ?\;H_2 \;(g)+ {\bf 1\;MgCl_2}\;(aq)$ .

The number of $\rm Mg$ and $\rm Cl$ atoms shall be the same on both sides. Therefore

$\rm {\bf 1\;Mg}\;(s) + {\bf 2\;HCl}\;(aq) \to ?\;H_2 \;(g)+ {1\;\underset{\wedge}{Mg}\underset{\wedge}{Cl_2}}\;(aq)$ .

The number of $\rm H$ atoms shall also conserve. Hence the equation:

$\rm {1\;Mg}\;(s) + {2\;\underset{\wedge}{H}Cl}\;(aq) \to {\bf 1\;H_2 \;(g)}+ {1\;MgCl_2}\;(aq)$ .

How many moles of HCl are available?

$M(\rm HCl) = 1.008 + 35.45 = 36.458\;g\cdot mol^{-1}$ .

$\displaystyle n({\rm HCl}) = \frac{m(\text{HCl})}{M(\text{HCl})} = \rm \frac{165.0\;g}{36.458\;g\cdot mol^{-1}} = 4.52576\;mol$ .

How many moles of Hydrogen gas will be produced?

Refer to the balanced chemical equation, the coefficient in front of $\rm HCl$ is 2 while the coefficient in front of $\rm H_2$ is 1. In other words, it will take two moles of $\rm HCl$ to produce one mole of $\rm H_2$ . $\rm 4.52576\;mol$ of $\rm HCl$ will produce only one half as much $\rm H_2$ .

Alternatively, consider the ratio between the coefficient in front of $\rm H_2$ and $\rm HCl$ is:

$\displaystyle \frac{n(\text{H}_2)}{n(\text{HCl})} = \frac{1}{2}$ .

$\displaystyle n(\text{H}_2) = n(\text{HCl})\cdot \frac{n(\text{H}_2)}{n(\text{HCl})} = \frac{1}{2}\;n(\text{HCl}) = \rm \frac{1}{2}\times 4.52576\;mol = 2.26288\;mol$ .

What will be the volume of that many hydrogen gas?

One mole of an ideal gas occupies a volume of 22.4 liters under STP (where the pressure is 1 atm.) On certain textbook where STP is defined as $\rm 1.00\times 10^{5}\;Pa$ , that volume will be 22.7 liters.

$V(\text{H}_2) = \rm 2.26288\;mol\times 22.4\;L\cdot mol^{-1} = 50.69\; L$ , or

$V(\text{H}_2) = \rm 2.26288\;mol\times 22.7\;L\cdot mol^{-1} = 51.37\; L$ .

The value "165.0 grams" from the question comes with four significant figures. Keep more significant figures than that in calculations. Round the final result to four significant figures.

5 0

3 years ago

What is the concentration if 20 grams of NaOH was dissolved in enough water to make a 250 mL NaOH solution?

gizmo_the_mogwai [7]

Answer: 1 molar NaOH contains 40 grams of NaOH per every liter of water

Explanation:

so 2 M NaOH contains twice that amount, ie. 80 grams per liter. Then, ine 250 ml of weater, there should be 80/4 = 20 grams of solid NaOH dissolved.

3 0

3 years ago