diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 641f8d7..4790706 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -5,7 +5,7 @@ ci:
 repos:
 
 - repo: https://github.com/pre-commit/pre-commit-hooks
-  rev: v3.4.0
+  rev: v4.1.0
   hooks:
   - id: check-ast
   - id: trailing-whitespace
@@ -30,12 +30,12 @@ repos:
     - python
 
 - repo: https://github.com/psf/black
-  rev: 21.12b0
+  rev: 22.3.0
   hooks:
   - id: black
 
 - repo: https://github.com/nbQA-dev/nbQA
-  rev: 0.8.0
+  rev: 1.3.1
   hooks:
   - id: nbqa-black
     additional_dependencies:
@@ -49,7 +49,7 @@ repos:
     - --nbqa-mutate
 
 - repo: https://github.com/macisamuele/language-formatters-pre-commit-hooks
-  rev: v2.1.0
+  rev: v2.3.0
   hooks:
   - id: pretty-format-ini
     args: [--autofix]
diff --git a/plasmapy_nei/nei/nei.py b/plasmapy_nei/nei/nei.py
index d05c169..c9ccac9 100644
--- a/plasmapy_nei/nei/nei.py
+++ b/plasmapy_nei/nei/nei.py
@@ -88,15 +88,15 @@ def __init__(
 
         self._number_densities = {
             elem: np.full((max_steps + 1, self.nstates[elem]), np.nan, dtype=np.float64)
-            * u.cm ** -3
+            * u.cm**-3
             for elem in self.elements
         }
 
         self._n_elem = {
-            elem: np.full(max_steps + 1, np.nan) * u.cm ** -3 for elem in self.elements
+            elem: np.full(max_steps + 1, np.nan) * u.cm**-3 for elem in self.elements
         }
 
-        self._n_e = np.full(max_steps + 1, np.nan) * u.cm ** -3
+        self._n_e = np.full(max_steps + 1, np.nan) * u.cm**-3
         self._T_e = np.full(max_steps + 1, np.nan) * u.K
         self._time = np.full(max_steps + 1, np.nan) * u.s
 
@@ -161,7 +161,7 @@ def _assign(
             }
 
             # Calculate the electron number density
-            n_e = 0.0 * u.cm ** -3
+            n_e = 0.0 * u.cm**-3
             for elem in elements:
                 integer_charges = np.linspace(
                     0, self.nstates[elem] - 1, self.nstates[elem]
@@ -920,7 +920,7 @@ def n_input(self) -> u.Quantity:
     def n_input(self, n: u.Quantity):
         if isinstance(n, u.Quantity):
             try:
-                n = n.to(u.cm ** -3)
+                n = n.to(u.cm**-3)
             except u.UnitConversionError:
                 raise u.UnitsError("Invalid hydrogen density.")
             if n.isscalar:
@@ -938,13 +938,13 @@ def n_input(self, n: u.Quantity):
                     bounds_error=False,
                     fill_value="extrapolate",
                 )
-                self._hydrogen_number_density = lambda time: f(time.value) * u.cm ** -3
+                self._hydrogen_number_density = lambda time: f(time.value) * u.cm**-3
                 self._n_input = n
         elif callable(n):
             if self.time_start is not None:
                 try:
-                    n(self.time_start).to(u.cm ** -3)
-                    n(self.time_max).to(u.cm ** -3)
+                    n(self.time_start).to(u.cm**-3)
+                    n(self.time_max).to(u.cm**-3)
                 except Exception:
                     raise ValueError("Invalid number density function.")
             self._n_input = n
diff --git a/plasmapy_nei/nei/tests/test_nei.py b/plasmapy_nei/nei/tests/test_nei.py
index bdf49d5..642e023 100644
--- a/plasmapy_nei/nei/tests/test_nei.py
+++ b/plasmapy_nei/nei/tests/test_nei.py
@@ -13,7 +13,7 @@
 
 time_array = np.array([0, 800]) * u.s
 T_e_array = np.array([4e4, 6e4]) * u.K
-n_array = np.array([1e9, 5e8]) * u.cm ** -3
+n_array = np.array([1e9, 5e8]) * u.cm**-3
 
 
 @pytest.fixture(
@@ -57,7 +57,7 @@
                 "inputs": inputs_dict,
                 "abundances": abundances,
                 "T_e": T_e_array,
-                "n": 1e9 * u.cm ** -3,
+                "n": 1e9 * u.cm**-3,
                 "time_input": time_array,
                 "time_start": 0 * u.s,
                 "time_max": 800 * u.s,
@@ -73,7 +73,7 @@
                 "inputs": inputs_dict,
                 "abundances": abundances,
                 "T_e": lambda time: 1e4 * (1 + time / u.s) * u.K,
-                "n": 1e15 * u.cm ** -3,
+                "n": 1e15 * u.cm**-3,
                 "time_max": 800 * u.s,
                 "max_steps": 2,
                 "dt": 100 * u.s,
@@ -87,7 +87,7 @@
                 "inputs": inputs_dict,
                 "abundances": abundances,
                 "T_e": 6e4 * u.K,
-                "n": lambda time: 1e9 * (1 + time / u.s) * u.cm ** -3,
+                "n": lambda time: 1e9 * (1 + time / u.s) * u.cm**-3,
                 "time_start": 0 * u.s,
                 "time_max": 800 * u.s,
                 "adapt_dt": False,
@@ -109,7 +109,7 @@
                     "Fe": 1e-4,
                 },
                 "T_e": 10001.0 * u.K,
-                "n": 1e13 * u.cm ** -3,
+                "n": 1e13 * u.cm**-3,
                 "time_max": 2e6 * u.s,
                 "tol": 1e-9,
                 "adapt_dt": False,
@@ -132,7 +132,7 @@
                     "S": 2e-6,
                 },
                 "T_e": 7e6 * u.K,
-                "n": 1e9 * u.cm ** -3,
+                "n": 1e9 * u.cm**-3,
                 "time_max": 1e8 * u.s,
                 "dt": 5e7 * u.s,
                 "max_steps": 3,
@@ -150,7 +150,7 @@
                 },
                 "abundances": {"H": 1, "He": 0.1, "O": 1e-4},
                 "T_e": 3e6 * u.K,
-                "n": 1e9 * u.cm ** -3,
+                "n": 1e9 * u.cm**-3,
                 "dt": 1e6 * u.s,
                 "time_start": 0 * u.s,
                 "time_max": 1e6 * u.s,
@@ -165,7 +165,7 @@
                 "inputs": ["H", "He"],
                 "abundances": {"H": 1, "He": 0.1},
                 "T_e": lambda t: u.K * (1e6 + 1.3e4 * np.sin(t.value)),
-                "n": 1e10 * u.cm ** -3,
+                "n": 1e10 * u.cm**-3,
                 "max_steps": 300,
                 "time_start": 0 * u.s,
                 "time_max": 2 * np.pi * u.s,