What Predicts the Element to Which an Atom Belongs?
The Periodic Table
The periodic tabular array shows all the elements and their concrete backdrop; it is bundled based on atomic numbers and electron configurations.
Learning Objectives
Identify the common periodic trends that can exist deduced from the periodic table of elements
Fundamental Takeaways
Key Points
- The periodic table lists all the elements, with data nigh their atomic weights, chemical symbols, and atomic numbers.
- The arrangement of the periodic table leads the states to visualize certain trends amid the atoms.
- The vertical columns (groups) of the periodic tabular array are arranged such that all its elements take the same number of valence electrons. All elements within a certain group thus share similar properties.
Primal Terms
- atomic number: The number, equal to the number of protons in an atom, that determines its chemical backdrop. Symbol: Z
- group: A vertical column in the periodic table, which signifies the number of valence crush electrons in an element'due south atom.
- catamenia: A horizontal row in the periodic tabular array, which signifies the total number of electron shells in an element's atom.
Element Symbols
The periodic table is structured as an 18 X 7 grid, positioned above a smaller double row of elements. The periodic table only lists chemical elements, and includes each isotope of each chemical element within one cell. In the typical periodic tabular array, each element is listed by its element symbol and atomic number. For example, "H" denotes hydrogen, "Li" denotes lithium, and and so on. Almost elements are represented by the beginning letter or first ii letters of their English proper name, but there are some exceptions. 2 notable exceptions include silver and mercury. The symbol for silvery is "Ag" from Latin argentum, which ways "gray" or "shining." The symbol for mercury is "Hg" from the Latinized Greek hydrargyrum, which means "h2o-argent." Many periodic tables include the full name of element as well and color-code the elements based on their stage at room temperature (solid, liquid, or gas).
The periodic table: The periodic tabular array is a tabular brandish of all the chemical elements. The atoms are grouped in gild of increasing atomic number.
Rows and Periods
The element symbol is always almost accompanied past other data such every bit atomic number and diminutive weight. Atomic number describes the number of protons in i cantlet of that element. For example, an atom of oxygen contains eight protons. Elements are listed in lodge of increasing diminutive number from left to right. Each row of the periodic table is chosen a menstruation and each column of the periodic table is called a group (or family). Some groups have specific names like the halogens or noble gases. Elements within the same period or group accept similar properties.
Determining Chemic Backdrop using the Periodic Table
Chemic properties of each element are adamant past the element's electronic configuration, and particularly by its outermost valence electrons. An chemical element's location in the periodic table is largely dependent on its electrons; the number of valence crush electrons determines its group, and the blazon of orbital in which the valence electrons prevarication in determines the element's cake. In addition, the full number of electron shells an atom determines which period it belongs to. Because of its structure, the periodic table has become an extremely useful tool for assessing and predicting elemental and chemic trends.
Molecules
Molecules are electrically neutral compounds made of multiple atoms bound together by chemical bonds.
Learning Objectives
Recognize the general properties of molecules
Key Takeaways
Cardinal Points
- Molecules are neutral and do not conduct any accuse.
- A molecule may consist of nonmetallic atoms of a single element, as with oxygen (O2), or of unlike elements, as with water (HiiO).
- The geometry and composition of a molecule volition decide its chemical and physical properties.
- Isomers are molecules with the same atoms in different geometric arrangements.
Fundamental Terms
- covalent: when ii or more nonmetallic atoms are bound together past sharing electrons.
- isomer: Molecules with the same number of atoms in unlike geometric arrangements.
- chemical compound: when two or more than different atoms are held together past a covalent bond. All compounds are molecules simply not all molecules are compounds.
- molecule: Two or more atoms that are held together by a chemical covalent bond.
Atoms and Molecules
An atom is defined equally a basic unit of matter that contains a centralized dumbo nucleus surrounded by an electron cloud. When ii or more atoms are held together by a chemical covalent bond, this new entity is known as a molecule. The word "molecule" is a loose term, and it colloquially carries different meanings across dissimilar fields of report. For example, the term "molecules" is used in the kinetic theory of gases, referring to whatever gaseous particle regardless of its limerick.
Most often, the term "molecules" refers to multiple atoms; a molecule may be composed of a single chemical element, as with oxygen (O2), or of multiple elements, such as water (HiiO). Molecules are neutral and carry no charge; this property distinguishes them from polyatomic ions, such as nitrate (NO3 –).
caffeine molecule: Caffeine is a complicated molecule, composed of many atoms bonded to each other in a specific arrangement.
Molecular size varies depending on the number of atoms that make up the molecule. Most molecules are also small to exist seen with the naked middle. The smallest molecule is diatomic hydrogen (H2), with a bond length of 0.74 angstroms. Macromolecules are large molecules equanimous of smaller subunits; this term from biochemistry refers to nucleic acids, proteins, carbohydrates, and lipids. Some macromolecules may be observed by specialized microscopes.
Oft, a chemical compound 's limerick can also be denoted by an empirical formula, which is the simplest integer ratio of its constituent chemic elements. However, this empirical formula does not ever describe the specific molecule in question, since it provides only the ratio of its elements. The total elemental composition of a molecule tin can exist precisely represented by its molecular formula, which indicates the exact number of atoms that are in the molecule.
Case
- C6H12Ovi = molecular formula for glucose
- CHtwoO = empirical (simplified ratio) formula for glucose
Isomers
Isomers are molecules with the same atoms in different geometric arrangements. Considering of these unlike arrangements, isomers often accept very different chemical and physical backdrop. In the picture below, 1-propanol is more often than not used in the synthesis of other compounds and has a less offensive odor, whereas 2-propanol is the common household alcohol.
propanol structural isomers: The chemical formula for propanol (C3H7OH) describes several different molecules, which vary by the position of the alcohol (OH). Each molecule is a structural isomer of the other.
Ions
An ion is an atom or molecule that has a net electric charge because its full number of electrons is non equal to its number of protons.
Learning Objectives
Compare the different classes of ions
Key Takeaways
Primal Points
- Ions are formed when the number of protons in an atom does not equal the number of electrons. If more protons are present, the ion is positive and is known as a cation; if more than electrons are present, the ion is negative and referred to as an anion.
- Ions are highly reactive species. They are generally constitute in a gaseous state and do not occur in abundance on Earth. They are repelled by similar electric charges and are attracted to opposite charges.
- The electron cloud of an atom determines the size of the atom; added electrons (anions) increment the electron repulsion, increasing the ion's size, while cations (with less electrons) are smaller than the atom because in that location are fewer electrons in the deject to repel each other.
Key Terms
- ion: An atom or group of atoms bearing an electrical charge, such every bit the sodium and chlorine atoms in a salt solution.
- anion: Ions that are negatively charged because they have more than electrons than protons.
- cation: Ions that are positively charged considering they take more than protons than electrons.
An atom is a basic unit of matter that consists of a dumbo nucleus composed of positively charged protons and neutral neutrons, which is surrounded by a deject of negatively charged electrons. If an atom has the same number of protons and electrons, it is electronically neutral. Even so, if the total number of electrons does not equal the number of protons, the atom has a cyberspace electric charge.
Any atom or molecule with a net charge, either positive or negative, is known equally an ion. An ion consisting of a single atom is a monoatomic ion; an ion consisting of 2 or more atoms is referred to as a polyatomic ion. The positive electric charge of a proton is equal in magnitude to the negative charge of an electron; therefore, the net electric charge of an ion is equal to its number of protons minus its number of electrons.
Ions are highly reactive species. They are mostly found in a gaseous state and do not occur in abundance on Earth. Ions in the liquid or solid state are produced when salts interact with their solvents. They are repelled by like electric charges and are attracted to opposite charges.
Types of Ions
In that location are specialized types of ions. Anions accept more than electrons than protons and so have a cyberspace negative accuse. Cations take more protons than electrons and so take a net positive charge. Zwitterions are neutral and have both positive and negative charges at unlike locations throughout the molecule. Anions are generally larger than the parent molecule or atom, because the backlog electrons repel each other and add to the physical size of the electron cloud. Cations are generally smaller than their parent cantlet or molecule due to the smaller size of their electron clouds.
Hydrogen ions: The relationship between a molecule, its cation, and its anion is shown.
An ion is denoted by writing its cyberspace negative charge in superscript immediately afterwards the chemical structure for the atom/molecule. Conventionally the internet charge is written with the magnitude before the sign; the magnitude of singly charged molecules/atoms is generally omitted. Monoatomic ions are sometimes besides represented past Roman numerals, which designate the formal oxidation state of the chemical element, whereas the superscripted numerals announce the cyberspace charge. For case, Atomic number 262+ tin can be referred to as Fe(II). These representations can exist thought of as equivalent for monoatomic ions, simply the Roman numerals cannot be applied to polyatomic ions.
Forming Ions
Ions can exist formed past ionization, which is the procedure of a neutral cantlet losing or gaining electrons. By and large, the electrons are either added to or lost from the valence vanquish of an atom; the inner-beat out electrons are more than tightly spring to the positively charged nucleus and so do non participate in this type of chemic interaction.
Ionization mostly involves a transfer of electrons between atoms or molecules. The process is motivated by the achievement of more stable electronic configurations, such as the octet rule, which states that most stable atoms and ions take eight electrons in their outermost (valence) shell. Polyatomic and molecular ions can as well be formed, generally by gaining or losing elemental ions, such equally H+, in neutral molecules. Polyatomic ions are generally very unstable and reactive.
An common example of an ion is Na+. Sodium has a +1 charge because sodium has eleven electrons. However, co-ordinate to the octet rule, sodium would be more stable with 10 electrons (2 in its inner most shell, 8 in its outermost shell). Therefore, sodium tends to lose an electron to become more stable. On the other manus, chlorine tends to gain an electron to become Cl–. Chlorine naturally has 17 electrons only it would be more stable with 18 electrons (2 in its inner most shell, 8 in its second shell, and 8 in its valence shell). Therefore, chlorine will take an electron from some other atom to go negatively charged.
Source: https://courses.lumenlearning.com/boundless-chemistry/chapter/the-periodic-table/
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