CHEMISTRY HIGH SCHOOL

What is first and second element of the periodic table?

Answers

Answer 1
Answer: The elements on the periodic table are listed in increasing atomic number. 

Hydrogen is the first element, and has an A.N. of 1. Also, its very interesting how it doesn't need 8 valence electrons to be stable. 

The second element is Helium, which has an A.N (atomic number) of two. 
Answer 2
Answer:

The first element of the periodic table is hydrogen (H), and the second element is helium (He).

Hydrogen, with atomic number 1, is the first element in the periodic table. It is the lightest and the most abundant element in universe. Hydrogen is a colorless, odorless gas and is the building block for all other elements.

Helium, with atomic number 2, is the second element in the periodic table. It is also a gas, but unlike hydrogen, it is inert and does not readily react with other elements. Helium is known for its low density, which makes it lighter than air, and it is commonly used for filling balloons and as a cooling medium in various scientific and industrial applications.

So, the first element of the periodic table is hydrogen (H), and the second element is helium (He).

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Related Questions

Calculate the change of enthalpy for the reaction CH4 (g) + NH3 (g) --> HCN (g) +3H2 (g) from the following reactions: Reaction 1: N2 (g) + 3H2 (g) --> 2NH3 (g) Change in enthalpy: -91.8 kJ/molReaction 2: C (s, graphite) + 2H2 (g) --> CH4 (g) Change in enthalply: -74.9 kJ/molReaction 3: H2 (g) + 2C (s, graphite) + N2 (g) --> 2HCN (g) Change in enthalpy: +270.3 kJ/molInclude the following:The numerical answer with correct units.State which reactions, if any, you had to "Flip".State which reactions you had to multiply, if any, to get the correct amount of the compound.
Which of the following statements is true for an exothermic reaction? The products have higher potential energy than the reactants, and the enthalpy change is negative. The products have higher potential energy than the reactants, and the enthalpy change is positive. The products have lower potential energy than the reactants, and the enthalpy change is negative. The products have lower potential energy than the reactants, and the enthalpy change is positive.
Concentrated nitric acid used in laboratory is 68 % nitric acid by mass in aqueous solution. What should be the molarity of such a sample of the acid if the density of the solution is 1.504 g mL-1?
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The diagram shows a model of an animal cell. Explain how you'd modify the model to show the structures in a plant cell.

The first periodic table developed by Mendeleev was not completely accurate, but was a great step toward accomplishing the periodic table of elements we use today. Explain how the modern periodic table is credible today because of Mendeleev’s work.

Answers

The answer is: elements in the same group of periodic system have similar properties.

Dmitri Mendeleev published a periodic table of the chemical elements in 1869.

Mendeleev noted gaps in the table and predicted then undiscovered elements existed eka-silicon (germanium) and eka-boron (scandium).

For example, germanium discovered in 1886 and it had proporties as Mendeleev predicted.

There are 118 unique substances (elements) arranged on an amazing chart that reveals their hidden secrets to anyone who knows how to read it.  

The first chemical element is hydrogen (atomic number is 1) and the last is oganesson (atomic number is 118).  

Elements are scheduled in periodic table, ordered by their atomic number.  
His periodic table provided everyone with the idea that elements should be arranged by the increasing order of their fundamental properties. It was later discovered that atomic number IS the fundamental property

H2O has a mc021-1.jpgHvap = 40.7 kJ/mol. What is the quantity of heat that is released when 27.9 g of H2O condenses?

Answers

The molecular weight of H2O is 18g/mol.
Therefore, 27.9 g H2O / (1mol/18g) = 0.155 mol H2O
Calculating only for the latent heat, the heat required to be released for this amount of H2O to condense is:
40.7 kJ/mol (0.155 mol) = 6.3 kJ or -6.3 kJ since it is to be released

What fluid flows very slowly?

Answers

Numerical modeling of coupled variably saturated fluid flow and reactive transport with fast and slow chemical reactions
Honey, at room temperature, has a higher viscosity and flows more slowly than water.

Which subatomic particle(s) are found in the nucleus of the atom?. Enter the subatomic particle or particles separated by commas.

Answers

The subatomic particles found in the nucleus of the atom are:

Protons, Neutrons
The subatomic particles found inside the nucleons of the atoms are also referred to as the "nucleons". The nucleons are the protons, which are positively charged,  and neutrons, which are neutral. The negatively charged subatomic particles, electrons, are found outside the nucleus. 

To calculate the amount of heat absorbed as a substance melts, which of the following information is NOT needed?a.
the mass of the substance
c.
the change in temperature
b.
the specific heat of the substance
d.
the density of the sample

Answers

To calculate the amount of heat absorbed as a substance melts, the information which we don't need is density.

What is the formula to calculate absorbed heat?

The formula which we used to calculate the amount of involved heat in a chemical reaction is:

Q = mcΔT, where

  • Q = absorbed heat
  • m = mass
  • c = specific heat
  • ΔT = change in temperature

Hence the information which we don't need is density.

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The answer is d. hope it helps!

An igneous rock originally has 3 grams of uranium 238 in it. When dated the rock only contains 1.8 grams. What are the parent and daughter concentrations (in percentages) and what is its age?

Answers

Answer :

The parent and daughter concentrations (in percentages) is, 60 % and 40 % respectively.

The age of rock is 3.32* 10^9\text{ years}

Explanation :

First we have to calculate the parent and daughter concentrations (in percentages).

\text{Parent concentrations}=(1.8g)/(3g)* 100=60\%

and,

\text{Daughter concentrations}=((3-1.8)g)/(3g)* 100=40\%

As we know that, the half-life of uranium-238 = 4.5* 10^9 years

Now we have to calculate the rate constant, we use the formula :

k=(0.693)/(t_(1/2))

k=\frac{0.693}{4.5* 10^9\text{ years}}

k=1.54* 10^(-10)\text{ years}^(-1)

Now we have to calculate the time passed.

Expression for rate law for first order kinetics is given by:

t=(2.303)/(k)\log(a)/(a-x)

where,

k = rate constant  = 1.54* 10^(-10)\text{ years}^(-1)

t = time passed by the sample  = ?

a = initial amount of the reactant  = 3 g

a - x = amount left after decay process = 1.8 g

Now put all the given values in above equation, we get

t=(2.303)/(1.54* 10^(-10))\log(3)/(1.8)

t=3.32* 10^9\text{ years}

Therefore, the age of rock is 3.32* 10^9\text{ years}
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