Write the chemical symbols for three different atoms or atomic anions with 18 electrons.

Three different atoms or atomic anions with 18 electrons: Cl⁻, K⁺, Ar

The Atomic Number (Z) indicates the number of protons in an atom of an element. If the atom is neutral then the number of protons will be equal to the number of electrons. So the atomic number can also indicate the number of electrons.

 So atomic number = number of protons = number of electrons

Mass Number (A) is the sum of protons and neutrons

Mass Number (A) = Number of protons + Number of Neutrons

So that the relationship between atomic numbers and mass numbers can be formulated as follows:

Atomic Number (Z) = Mass Number (A) - Number of Neutrons

In the following element notation,

Information

X = symbol of elemental atom

A = mass number

  = number of protons + number of neutrons

Z = atomic number

  = number of protons = number of electrons, on neutral elements

In an atom, there are levels of energy in the skin and sub skin.

This energy level is expressed in the form of electron configurations.

Charging electrons in the sub skin uses the following sequence:

1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5p⁶, 6s², etc.

The location of the element group in the periodic system is determined by the number of valence electrons that fills the last sub-skin

The element period is determined from the valence shell (the largest main quantum number (n))

Atoms or ionic atoms that have 18 electrons include:

a. Cl: 1s² 2s² 2p⁶ 3s² 3p⁵

because it captures 1 more electron to be stable like the noble gas Ar so that the electron configuration has 18 electrons

Cl-: 1s² 2s² 2p⁶ 3s² 3p⁶

b. S: 1s² 2s² 2p⁶ 3s² 3p⁴

catch 2 electrons to be stable

S²⁻: 1s² 2s² 2p⁶ 3s² 3p⁶

c. K: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

release 1 electron to stabilize it

K⁺: 1s² 2s² 2p⁶ 3s² 3p⁶

d. Ca: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

release 2 electrons to stabilize

Ca²⁺: 1s² 2s² 2p⁶ 3s² 3p⁶

While the notation of the symbol elements are:

element symbol

link

the chemical symbols

link

Identify the group number

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Keywords: the chemical symbols, electron configuration

plants need sunlight, water, and carbon dioxide to make food. plants use the raw materials of water, nutrients they absorb from soil, and carbon dioxide to make sugars the plant can use. energy from the sun and chlorophyll are also needed.

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol