CHEM 101 Lecture Notes - Lecture 1: Atomic Number, Chemical Formula, Mass Number

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20 Jan 2017

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Element- The simplest form of matter and in its pure state contains only one type of atom. They

are classified according to their chemical properties.

Symbols of elements

-They are organized in the periodic table

- Elements are represented by chemical symbols

-Most symbols begin with the first letter, first two letter, or first and third letter.

-Rule: Only first letter in the Elements symbol is capitalized

Finding elements

-8 horizontal rows

-18 vertical columns

-main group elements are the first two columns and the last six of the periodic table labeled I

through VIII. Called representative elements

Compound- is represented by combining two or more elemental symbols together. The

chemical formula shows the elements the compound contains and the number of atoms of each

element.

Ex: NaCl one Sodium One Chlorine

Atomic number and the periodic table

The number of the element is called the atomic number. The atomic number tells us the identity

of the element. The periodic table organizes elements by their atomic number.

A look inside the atom

-Subatomic particles are found inside the atom

-chemists are concerned with three subatomic particles

-Protons positively charged

- Neutrons neutral

-electrons negatively charged

Protons

-are positively charged

-positive+negative=neutral

-protons and electrons make up the atoms

Neutrons

-electrically neutral

-same mass as a proton

-This explains why the atomic mass is much heavier than the mass of protons+electrons

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Document Summary

Element- the simplest form of matter and in its pure state contains only one type of atom. They are classified according to their chemical properties. Most symbols begin with the first letter, first two letter, or first and third letter. Rule: only first letter in the elements symbol is capitalized. Main group elements are the first two columns and the last six of the periodic table labeled i through viii. Compound- is represented by combining two or more elemental symbols together. The chemical formula shows the elements the compound contains and the number of atoms of each element. The number of the element is called the atomic number. The atomic number tells us the identity of the element. The periodic table organizes elements by their atomic number. This explains why the atomic mass is much heavier than the mass of protons+electrons. The nucleus is dense, it contains most of the mass of the atom.

Related Questions

This question reviews the format for writing an element's written symbol. Recall that written symbols have a particular format. Written symbols use a form like this: ^35_17 Cl In this form the mass number, 35, is a stacked superscript. The atomic number, 17, is a stacked subscript. "Cl" is the chemical symbol for the element chlorine. A general way to show this form is: ^mass number_atomic number Symbol It is also correct to write symbols by leaving off the atomic number, as in the following form: ^35Cl or mass number Symbol This is because if you write the element symbol, such as Cl. you know the atomic number is 17 from that symbol. Remember that the atomic number, or number of protons in the nucleus, is what defines the element Thus, if 17 protons are in the nucleus, the element can only be chlorine. Sometimes you will only see ^35Cl, where the atomic number is not written. Watch this video to review the format for written symbols. In the following table each column represents a neutral atom. Fill in the gaps in the following table by working this problem out on a separate sheet of paper. You will need the periodic table in the "resources' drop down menu in the upper right hand corner of this question to look up atomic numbers and masses. Use the hints in the following part whenever needed to review the steps to filling in this type of table. Once you have filled in all the gaps on a separate sheet of paper, enter the four missing element symbols in the first row of the table into the answer box below. You can open the first hint to view a video that steps you through filling in the first column of the table. Enter the four missing symbols for the first row of the table from left to right, separated by commas, into the answer box below. Use the stacked super/ subscripts button (available in the templates button menu above the answer entry box) to enter the symbols in the following form: ^mass number_atomic number Symbol, or for example, ^35_17 Cl. Express your answers as chemical symbols.

Place the elements in their proper position on the periodic table. To make this more challenging. I have not included their identities. Instead of the usual chemical symbol, each element is represented by a code letter. Some clues to the element's identities are listed below. In addition, the elements fall into these families or groups.

JKQ, WNVG, IAL, EPFZ, YBR, ODS, CXU, THM

Place each code letter in its proper space in the table below. Indicate the actual chemical symbol that corresponds to each letter.

V is an inert gas

E is an alkali metal

U is a halogen

D is in family VA

J is an alkaline earth metal

T is in family VIA

R has one less proton than A

A has six protons in its nucleus

R has an atomic number one more than J

O has an atomic number one more than A

S has 8 more protons in its nucleus than D

F has only one proton in each atom

Y has atoms that are larger than the atoms of B

I has the largest atomic number in its group

T is found in the fourth period

C has atoms that are larger than those of U, but smaller than those of X

V has one more proton in its nucleus that U

H has the smallest atomic number in its family

G has two protons in each atom

N is a third-period element

Q has an atomic mass greater than that of J and less than that of K

E has an atomic number less than that of Z, but greater than that of J

Z has more protons than other elements in its family

U is found in the second period

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CHEM 101 Lecture Notes - Lecture 1: Atomic Number, Chemical Formula, Mass Number

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