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JulsSmile [24]
3 years ago
8

Help Me Please

Chemistry
2 answers:
GaryK [48]3 years ago
6 0

in the periodic table, elements are classified in the ascending order of their atomic numbers. atomic number is the number of protons

in elements the number of protons is equal to the number of electrons

the condensed notation of electron configuration is when the symbol of the noble gas closest to the elements electron configuration is mentioned.

[He] 2s² - number of electrons in He is 2 , and 2 more electrons in the s subshell adds upto a sum of 4 electrons. number of protons = number of electrons

then number of protons = 4

then atomic number is 4. element with atomic number 4 is Be

the element is Be


[Ne] 3s² 3p⁵

Ne atomic number is 10. 10 + 7 electrons in the third shell = 17 electrons in total

atomic number - 17 is Cl

element is Cl


[Xe] 6s¹

Xe atomic number is 54, 54 + 1 electron in the sixth shell = 55 electrons in total

atomic number of 55 is Cs

element is Cs


[Ar] 4s² 3d⁹

Ar atomic number is 18. 18 + 2 electrons in 4th shell and 9 in d subshell of 3rd shell = 29 electrons in total

atomic number of 29 is Cu

element is Cu

Shtirlitz [24]3 years ago
6 0
[He]2s2: Be
[Ne]3s23p5: Cl
[Xe]6s1: Cs
<span> [Ar]4s23d9: Cu</span>
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balu736 [363]

Answer:

51.53 grams .

Explanation:

Na₃PO₄    ⇄  3Na⁺¹   +    PO₄⁻³ .

1 mole           3 mole

725 mL of 1.3 M Na⁺  ions

= .725 x 1.3 moles of Na⁺ ions

= .9425 moles

3 mole of Na⁺  is formed by 1 mole of Na₃PO₄

.9425 mole of Na⁺  is formed by .9425/3  mole of Na₃PO₄

Na₃PO₄ needed =  .9425/3  moles = .3142 moles

Molecular weight of Na₃PO₄ = 164

grams of Na₃PO₄ needed = .3142 x 164 = 51.53 grams .

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2 years ago
Find the percentage of mass in each of the element Ca ( HCO3)2 (Ca= 40, H = 1, O = 16, C= 35)​
Alex787 [66]

Answer:

% Ca = 24.69%

% H = 1.2%

% C = 14.8%

% O = 59.25%

Explanation:

The percentage by mass of each element can be calculated by dividing the mass of each element in the compound by the molar mass of the compound.

Molar mass of Ca(HCO3)2

Where; (Ca= 40, H = 1, O = 16, C= 12)

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- % mass of Ca = 40/162 × 100

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- % mass of C = 24/162 × 100

= 0.148 × 100

= 14.8%

- % mass of O = 96/162 × 100

= 0.5925 × 100

= 59.25%

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