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Ira Lisetskai [31]
3 years ago
5

A single atom of an element has 21 neutrons, 20 electrons, and 20 protons. Which element is it?

Chemistry
1 answer:
jeyben [28]3 years ago
5 0

Answer:

Calcium

Explanation:

Clacium has atomic number 20. The atomic number. This means that it has 20 protons and 20 electrons. it has 21 neutrons.

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Speed of Light Math Quiz (20 points)
Goryan [66]

The wavelength of light : 4.14 x 10⁻⁵ m

<h3>Further explanation </h3>

Radiation energy is absorbed by photons

The energy in one photon can be formulated as

\large{\boxed{\bold{E\:=\:h\:.\:f}}}

Where

h = Planck's constant (6,626.10⁻³⁴ Js)

f = Frequency of electromagnetic waves

The energy of the light = 4.8 x 10⁻²¹ J

The wavelength of light :

\tt E=h.\dfrac{c}{\lambda}\\\\\lambda=\dfrac{h.c}{E}\\\\\lambda=\dfrac{6.626.10^{-34}\times 3.10^8}{4.8.10^{-21}}\\\\\lambda=4.14.10^{-5}~m

4 0
3 years ago
Organize the following list of atoms from lowest to highest Electronegativity:
Anon25 [30]

Answer:

Barium<Strontium<Calcium <Magnesium< Beryllium

Explanation:

Electronegativity is defined as the ability of an atom in a bond to attract the shared electrons of the bond towards itself.

Electronegativity is a periodic trend that decreases down the group and increases across the period.

Hence, if i want to arrange Beryllium, Barium, Strontium, Magnesium, Calcium in order of increasing electronegativity, i will have;

Barium<Strontium<Calcium <Magnesium< Beryllium

5 0
3 years ago
How many grams of mercury are needed to react completely with 157g of sulfur to form hgs?
Salsk061 [2.6K]
<span>To solve this we need to balance the equations first.
 So Hg + S --> HgS is balanced
 One mole of Hg requires one mole of S to form one mole of HgS.
 Number of moles of Sulphur = mass/ molar mass = 157/32 = 4.906
So 4.90 moles of S reacts with 4.90 moles of Hg.
Hence there are 4.90 moles of 4.90 of Hg.
 Mass = number of moles * molar mass of Hg
Mass = 4.906 * 200.59 = 982.891g</span>
8 0
3 years ago
Read 2 more answers
calculate the difference in slope of the chemical potential against temperature on either side of the normal freezing point of w
kipiarov [429]

Answer:

(a) The normal freezing point of water (J·K−1·mol−1) is -22Jmole^-^1k^-^1

(b) The normal boiling point of water (J·K−1·mol−1) is -109Jmole^-^1K^-^1

(c) the chemical potential of water supercooled to −5.0°C exceed that of ice at that temperature is  109J/mole

Explanation:

Lets calculate

(a) - General equation -

      (\frac{d\mu(\beta )}{dt})p-(\frac{d\mu(\alpha) }{dt})_p = -5_m(\beta )+5_m(\alpha ) =  -\frac{\Delta H}{T}

 \alpha ,\beta → phases

ΔH → enthalpy of transition

T → temperature transition

 (\frac{d\mu(l)}{dT})_p -(\frac{d\mu(s)}{dT})_p == -\frac{\Delta_fH}{T_f}

            = \frac{-6.008kJ/mole}{273.15K} ( \Delta_fH is the enthalpy of fusion of water)

           = -22Jmole^-^1k^-^1

(b) (\frac{d\mu(g)}{dT})_p-(\frac{d\mu(l)}{dT})_p= -\frac{\Delta_v_a_p_o_u_rH}{T_v_a_p_o_u_r}

                                  = \frac{40.656kJ/mole}{373.15K} (\Delta_v_a_p_o_u_rH is the enthalpy of vaporization)

                               = -109Jmole^-^1K^-^1

(c) \Delta\mu =\Delta\mu(l)-\Delta\mu(s) =-S_m\DeltaT

[\mu(l-5°C)-\mu(l,0°C)] =  [\mu(s-5°C)-\mu(s,0°C)]=-S_mΔT

\mu(l,-5°C)-\mu(s,-5°C)=-Sm\DeltaT [\mu(l,0

\Delta\mu=(21.995Jmole^-^1K^-^1)\times (-5K)

     = 109J/mole

6 0
3 years ago
Which statement best explains why the elements in Group 18 do not have electronegativity values?
Gnesinka [82]

Answer:

1) The elements have filled valence levels.

Explanation:

Since they have filled valence levels, they're stable and don't need to electrons to fill their valence shells since they're already full.

2) False, They do have electrons

3) False, He does have only one electron shell, but going down the periods, every next element have one more electron shell than a preceding one has.

4)False, they're actually the smallest atoms of their respective period

5 0
3 years ago
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