How Does an Element's Family Determine Its Number of Valence Electrons
The Periodic Table
The periodic table shows all the elements and their physical properties; it is bundled based on diminutive numbers and electron configurations.
Learning Objectives
Place the common periodic trends that can be deduced from the periodic table of elements
Key Takeaways
Fundamental Points
- The periodic table lists all the elements, with information nigh their atomic weights, chemical symbols, and atomic numbers.
- The arrangement of the periodic table leads us to visualize certain trends amongst the atoms.
- The vertical columns (groups) of the periodic table are bundled such that all its elements have the same number of valence electrons. All elements within a certain group thus share similar properties.
Key Terms
- atomic number: The number, equal to the number of protons in an cantlet, that determines its chemical properties. Symbol: Z
- group: A vertical column in the periodic table, which signifies the number of valence vanquish electrons in an element's atom.
- period: A horizontal row in the periodic table, 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 filigree, positioned above a smaller double row of elements. The periodic table only lists chemical elements, and includes each isotope of each element within one cell. In the typical periodic tabular array, each element is listed by its element symbol and atomic number. For instance, "H" denotes hydrogen, "Li" denotes lithium, and so on. Most elements are represented by the outset letter or first ii letters of their English proper noun, simply there are some exceptions. Two notable exceptions include silver and mercury. The symbol for silver is "Ag" from Latin argentum, which means "gray" or "shining." The symbol for mercury is "Hg" from the Latinized Greek hydrargyrum, which means "water-silver." Many periodic tables include the full name of chemical element also and color-lawmaking the elements based on their phase at room temperature (solid, liquid, or gas).
The periodic tabular array: The periodic table is a tabular display of all the chemic elements. The atoms are grouped in gild of increasing atomic number.
Rows and Periods
The chemical element symbol is e'er almost accompanied by other information such as diminutive number and atomic weight. Atomic number describes the number of protons in one atom of that element. For case, an cantlet of oxygen contains 8 protons. Elements are listed in guild of increasing atomic number from left to right. Each row of the periodic table is called a period and each cavalcade of the periodic table is chosen a group (or family). Some groups accept specific names like the halogens or noble gases. Elements within the same catamenia or group have similar properties.
Determining Chemical Properties using the Periodic Table
Chemical backdrop of each element are determined by the element's electronic configuration, and particularly by its outermost valence electrons. An element'south location in the periodic table is largely dependent on its electrons; the number of valence beat electrons determines its group, and the blazon of orbital in which the valence electrons lie in determines the element's block. In addition, the full number of electron shells an atom determines which period it belongs to. Because of its structure, the periodic tabular array has become an extremely useful tool for assessing and predicting elemental and chemical trends.
Molecules
Molecules are electrically neutral compounds made of multiple atoms bound together by chemical bonds.
Learning Objectives
Recognize the full general properties of molecules
Key Takeaways
Central Points
- Molecules are neutral and exercise not comport any charge.
- A molecule may consist of nonmetallic atoms of a unmarried chemical element, as with oxygen (O2), or of different elements, as with h2o (HtwoO).
- The geometry and composition of a molecule volition determine its chemical and physical properties.
- Isomers are molecules with the same atoms in dissimilar geometric arrangements.
Key Terms
- covalent: when 2 or more nonmetallic atoms are bound together by sharing electrons.
- isomer: Molecules with the same number of atoms in different geometric arrangements.
- compound: when two or more unlike atoms are held together by a covalent bond. All compounds are molecules but not all molecules are compounds.
- molecule: Two or more atoms that are held together by a chemic covalent bail.
Atoms and Molecules
An atom is defined every bit a basic unit of matter that contains a centralized dumbo nucleus surrounded by an electron cloud. When two or more atoms are held together by a chemical covalent bond, this new entity is known equally a molecule. The word "molecule" is a loose term, and it colloquially carries different meanings across different fields of report. For instance, the term "molecules" is used in the kinetic theory of gases, referring to any gaseous particle regardless of its limerick.
About often, the term "molecules" refers to multiple atoms; a molecule may be equanimous of a unmarried element, as with oxygen (Oii), or of multiple elements, such as water (H2O). Molecules are neutral and bear no accuse; this property distinguishes them from polyatomic ions, such every bit nitrate (NOiii –).
caffeine molecule: Caffeine is a complicated molecule, composed of many atoms bonded to each other in a specific organisation.
Molecular size varies depending on the number of atoms that make up the molecule. Most molecules are too small to exist seen with the naked eye. 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.
Frequently, a chemical compound 'southward composition can as well exist denoted by an empirical formula, which is the simplest integer ratio of its constituent chemical elements. Nonetheless, this empirical formula does not always describe the specific molecule in question, since it provides just the ratio of its elements. The full elemental limerick of a molecule can exist precisely represented by its molecular formula, which indicates the exact number of atoms that are in the molecule.
Instance
- C6H12O6 = molecular formula for glucose
- CHtwoO = empirical (simplified ratio) formula for glucose
Isomers
Isomers are molecules with the same atoms in unlike geometric arrangements. Because of these different arrangements, isomers often take very different chemical and physical properties. In the pic below, 1-propanol is mostly used in the synthesis of other compounds and has a less offensive scent, whereas 2-propanol is the mutual household booze.
propanol structural isomers: The chemical formula for propanol (C3HviiOH) describes several unlike 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 electrical accuse because its total number of electrons is not equal to its number of protons.
Learning Objectives
Compare the dissimilar classes of ions
Key Takeaways
Central Points
- Ions are formed when the number of protons in an cantlet does not equal the number of electrons. If more than protons are present, the ion is positive and is known as a cation; if more electrons are present, the ion is negative and referred to as an anion.
- Ions are highly reactive species. They are more often than not plant in a gaseous state and do not occur in abundance on Earth. They are repelled by like electrical charges and are attracted to reverse 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 considering in that location are fewer electrons in the cloud to repel each other.
Key Terms
- ion: An atom or grouping of atoms begetting an electric charge, such as the sodium and chlorine atoms in a salt solution.
- anion: Ions that are negatively charged considering they have more electrons than protons.
- cation: Ions that are positively charged because they have more protons than electrons.
An atom is a basic unit of thing that consists of a dense nucleus composed of positively charged protons and neutral neutrons, which is surrounded by a cloud of negatively charged electrons. If an cantlet has the aforementioned number of protons and electrons, it is electronically neutral. However, if the total number of electrons does not equal the number of protons, the atom has a net electrical charge.
Whatsoever atom or molecule with a net charge, either positive or negative, is known as an ion. An ion consisting of a single atom is a monoatomic ion; an ion consisting of two or more atoms is referred to every bit 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 generally found in a gaseous state and practise non occur in abundance on World. Ions in the liquid or solid state are produced when salts collaborate with their solvents. They are repelled past like electrical charges and are attracted to opposite charges.
Types of Ions
There are specialized types of ions. Anions take more electrons than protons then have a net negative charge. Cations have more protons than electrons and so accept a cyberspace positive accuse. Zwitterions are neutral and have both positive and negative charges at different locations throughout the molecule. Anions are generally larger than the parent molecule or atom, considering the excess electrons repel each other and add to the physical size of the electron cloud. Cations are mostly 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 past writing its net negative charge in superscript immediately afterward the chemical construction for the atom/molecule. Conventionally the internet charge is written with the magnitude before the sign; the magnitude of singly charged molecules/atoms is mostly omitted. Monoatomic ions are sometimes also represented by Roman numerals, which designate the formal oxidation country of the chemical element, whereas the superscripted numerals denote the net accuse. For example, Atomic number 26two+ tin exist referred to as Fe(2). These representations can exist idea of every bit equivalent for monoatomic ions, merely the Roman numerals cannot be applied to polyatomic ions.
Forming Ions
Ions can be formed by ionization, which is the process of a neutral atom losing or gaining electrons. Generally, the electrons are either added to or lost from the valence beat of an atom; the inner-beat electrons are more tightly bound to the positively charged nucleus and and so do not participate in this type of chemical interaction.
Ionization generally involves a transfer of electrons betwixt atoms or molecules. The process is motivated past the accomplishment of more than stable electronic configurations, such as the octet rule, which states that most stable atoms and ions accept viii electrons in their outermost (valence) shell. Polyatomic and molecular ions can also be formed, mostly by gaining or losing elemental ions, such equally H+, in neutral molecules. Polyatomic ions are by and large very unstable and reactive.
An mutual instance of an ion is Na+. Sodium has a +1 charge because sodium has xi electrons. Still, according to the octet dominion, sodium would be more stable with 10 electrons (2 in its inner near vanquish, eight in its outermost beat). Therefore, sodium tends to lose an electron to become more stable. On the other hand, chlorine tends to gain an electron to get Cl–. Chlorine naturally has 17 electrons only it would be more stable with 18 electrons (2 in its inner virtually shell, 8 in its second shell, and 8 in its valence beat out). Therefore, chlorine volition have an electron from another cantlet to become negatively charged.
Source: https://courses.lumenlearning.com/boundless-chemistry/chapter/the-periodic-table/
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