An atom of plutonium (Figure 2), which has 94 protons (thus an atomic number of 94), has electrons all the way out into the seventh shell. The sixth can hold up to eight or 18, and the seventh (and last) shell either two or 18. The third shell from the center can hold up to 18, and the fourth and fifth 32 each. The next shell can hold up to eight electrons. Compare an atom to our solar system for a minute: The sun is analogous to the nucleus of an atom where protons and neutrons are found, the planets revolving around the sun are analogous to electrons.Ītomic theory tells us that the innermost shell nearest the nucleus can contain no more than two electrons. The electrons are arranged in shells, a term used to describe the orbits of electrons around the nucleus. Atoms have electrons whirling around their nucleus, which contains protons and usually neutrons. One more thing about atoms before we discuss the formation of compounds, like water. Neutrons give an atom weight but do not alter its ionic charge. The elements deuterium (one neutron) and tritium (two neutrons) are isotopes of hydrogen. However, if a neutron happens to be present in the atom’s nucleus, or center, we call that an isotope of hydrogen. Hydrogen in its purest form has one electron and one proton. Most atoms also have neutrons, which are not charged (neutral). Because an atom of hydrogen can share its electron with other elements easily, hydrogen can bond with atoms of other elements, forming what is known as an ionic bond.Īll atoms have positively charged protons and negatively charged electrons. An atom of hydrogen is made of one proton and one electron (Figure 1), and donates (or shares) its electron easily.

PH is commonly used to describe the activity of the hydrogen ion. PH above 7.0 is considered alkaline (or basic). PH 7.0 is considered neutral, or balanced it has the same amount of acid and base ions. PH is the measurement of the activity of free hydrogen (H+, acid) and hydroxyl (OH-, base) ions in a solution. If we grab a sample of treatment plant influent or effluent and measure the pH, what we’re really measuring is the balance of the amount of acid and base chemicals in that water. So, you’re probably asking: What the heck does that mean? If we look at what pH represents, we find that it is the measurement of how acidic or alkaline (basic) a solution is. The technical definition of pH is: the logarithm of the reciprocal of the hydrogen ion activity in a given solution. Let’s look at those matters - and explore how questions about pH might be worded on a wastewater licensing exam. When operators are asked to define pH, many struggle to describe what it is and how it is measured. Get Laboratory articles, news and videos right in your inbox! Sign up now.

Sewage effluent definition