Chemisattempt is defined as the methodical investigation of the properties, structure, and also actions of matter and also the changes issue undergoes. This general interpretation raises many questions. These concerns are answered in the examine of chemistry. Terms and basic concepts that aid in knowledge chemisattempt will be discussed in this chapter.

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EO 1.1

DEFINE the adhering to terms:

 

 

a.

States of matter

d.

Mole

 

b.

Atomic weight

e.

Gram atomic weight

 

c.

Molecular weight

f.

Gram molecular weight

EO 1.2 LIST the components of an atom, their relative sizes, and also charges.

EO 1.3 STATE the criterion used to classify an atom chemically.

Characteristics of Matter

The term states of matter refers to the physical creates in which matter exists: solid, liquid, and gas. Solids are identified as having both a definite shape and a definite volume. In a solid, the forces that save the molecules or atoms together are strong. Therefore, a solid does not need outside support to maintain its shape.

Liquids have definite quantities however indefinite shapes and also are slightly compressible. Liquids take the shape of their containers. The forces that keep a liquid"s molecules or atoms together are weaker than in the solids.

Gases are conveniently compressible and capable of unlimited growth. They have indefinite form and indefinite volume. Of the three says, gases have the weakest forces holding their molecules or atoms together.

The different states of matter have actually one thing in common; they have the right to all be damaged down right into basic devices referred to as atoms.


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CHARACTERISTICS OF ATOMS

Fundamentals of Chemistry

 

 

 

The Atom Structure

All matter is composed of atoms, existing individually or in combicountry with each various other. An atom is an extremely small electrically-neutral ppost. It is the smallest unit associated in the chemical readjust of matter. Atoms can be treated as distinct pwrite-ups bereason they behave actually as such chemically, yet atoms themselves are written of also smaller subparts. Understanding these atomic subpshort articles is important in knowledge chemisattempt.

An atom is written of a positively-charged nucleus orbited by one or more negatively-charged particles referred to as electrons. A simplified schematic representation of this setup is depicted in Figure 1. The nucleus is the core of an atom. It has a positive charge bereason it typically consists of two pwrite-ups, the neutron and the proton (hydrogen is the exception via just a proton in the nucleus). The neutrons are electrically neutral, and also the protons are electrically positive. A nucleus with one proton has actually a charge of +1 (or simply 1), and also a nucleus with 2 prolots has a +2 charge. With Each Other the neutrons and also prolots provide the nucleus its mass, but the proton alone provides the nucleus its positive charge.

Neutrons and also proloads are fairly huge and also are fundamentally equal in mass.

Figure 1 Schematic of a Simple Atom (Helium)


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Fundamentals of Chemistry

CHARACTERISTICS OF ATOMS

 

 

 

The pposts that orbit the nucleus are electrons. They are extremely little, with a mass only 1/1835 the mass of a proton or neutron. Each electron is negatively charged, and the charge of one electron is equal in magnitude (yet opposite in sign) to the charge of one proton. The number of electrons orbiting a nucleus is precisely equal to the number of prolots had in that nucleus. The equal and also oppowebsite charges cancel each various other, and also the atom in its entirety is neutral. The electrons are bound in the atom by electrostatic attractivity. The atom stays neutral unless some exterior force causes a readjust in the number of electrons.

The diameter of the atom is identified by the array of the electrons in their travels roughly the nucleus and is around 10-8 cm. The diameter of the nucleus is around 10,000 times smaller, roughly 10-13 to 10-12 cm. Because the nucleus is written of neutrons and proloads that are around 1835 times heavier than an electron, the nucleus consists of nearly all the mass of the atom, but constitutes a really little fraction of the volume. Although electrons are individually exceptionally tiny, the area in which they orlittle the nucleus constitutes the biggest component of the atomic volume.

Figure 1 illustrates these dimension relationships, however not to scale. If the nucleus were the dimension shown, the electrons would be several hundred feet ameans.

Some of the properties of the atom and also its component parts are summarized in Table 1. The masses noted in Table 1 are measured in atomic mass systems (amu), which is a family member scale in which the mass of a proton is around 1.0.

TABLE 1

Properties of the Atom and its Fundamental Particles

Pshort article Name

Relative Mass

Relative Charge

 

(amu)

(based upon charge of proton)

Electron

0.00055 or 1/1835

-1

Proton

1.0

1

Neutron

1.0

0

Chemical Elements

An atom is classified chemically by the number of prolots in its nucleus. Atoms that have actually the same variety of proloads in their nuclei have actually the very same chemical actions. Atoms that have the same variety of prolots are grouped together and also constitute a chemical aspect.


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CHARACTERISTICS OF ATOMS

Fundamentals of Chemistry

 

 

 

Chemical Symbols

At one time chemists provided assorted symbols, equivalent to shorthand also, for the atoms of the different elements. These icons were extremely cumbersome and were replaced by abbreviations of the names of the facets. Each element has actually been assigned a particular one or two letter symbol based upon the first letter of its chemical name. Because tbelow are several facets with the very same initially letter, it is regularly vital to include the second letter to the symbol. In some situations the symbol comes from an abbreviation for the old latin name of the facet. For example, Fe represents iron (ferrum) and Cu for copper (cuprum). The initially letter of the chemical symbol is always capitalized. If the symbol has 2 letters, the second letter is constantly lowersituation.

Atomic Number

The variety of prolots in the nucleus plays such a crucial duty in identifying the atom that it is provided a unique name, the atomic number. The symbol Z is frequently used for atomic number (or variety of protons). Hydrogen has an atomic number of 1 and also lawrencium has actually an atomic variety of 103. The atomic number is likewise equal to the number of electrons.

Atomic Mass Number

The sum of the complete variety of protons, Z, and also the full variety of neutrons, N, is dubbed the atomic mass number. The symbol is A. Not all atoms of the very same aspect have the very same atomic mass number, bereason, although the Z is the very same, the N and for this reason the A are different. Atoms of the same aspect through various atomic mass numbers are dubbed isotopes.

Atomic Weight

In Table 1, the masses of atomic pwrite-ups are provided in atomic mass units (amu). These units recurrent a family member range in which the mass of the isotope carbon-12 is offered as the traditional and all others are regarded it. Specifically, 1 amu is identified as 1/12 the mass of the carbon-12 atom. Due to the fact that the mass of a proton or a neutron is around 1 amu, the mass of a certain atom will certainly be roughly equal to its atomic mass number, Z.

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The atomic weight of an aspect is generally even more beneficial than isotopic masses. The atomic weight of an element is defined as the weighted average of the masses of every one of its organic occurring isotopes. The atomic weight of the facets are listed in Table 2. The elements that have their atomic weights in parentheses are unsteady. For these facets, the atomic weight of the longest living isotope is supplied fairly than the average of the masses of all developing isotopes.